Online Team Teaching as the Predictive Power of Iranian EFL Learners’ Grammar Achievement

As one of the recent and motivating teaching methods, this research aimed to study team teaching as its focus. The study investigated any significant effect of team teaching on English as a Foreign Language (EFL) Iranian learners’ grammar. Two classes of 25 learners (Experimental and control groups) were held. In these classes, 10 grammar tenses were chosen by the institute through learners’ weaknesses, such as present simple, present continuous, past simple, past continuous


Introduction
Learning a foreign language, especially English language as an international one, to communicate appropriately in today's technological communicative era is known as one of the main 21stcentury skills. Accordingly, grammar is one of the most important components of foreign language learning since it is considered a prerequisite in speaking and writing. Besides, Sawir (2005) asserted that grammar is one of the toughest areas in teaching and learning English, and knowing the grammar aids language learners to speak a lot. Zhang (2009) also argues that grammar and vocabulary form the organization of the English language because grammar and vocabulary are the basis of the English language. Similarly, in the Iranian context, Salehi and Hesabi (2014) reported that grammar teaching and learning seem to be vital, particularly for adult learners in any language teaching curriculum, since to learn English, students have to be able to use suitable grammar structures.
However, despite the vital role of grammar in language teaching and learning, one of the major challenges teachers face in foreign language settings is making students excited about grammar. It is often because the grammar exercises and the approaches to teaching them are not so interesting and English as a Foreign Language (EFL) learners do not try to use grammatical structures in their productive skills like speaking and writing. In this regard, Aslani and Tabrizi (2015) also stated that learning grammar is not an enjoyable or easy task for students to handle. Teachers are even bored with their students' constant complaints about the problems they have in learning and applying what they have learned in their speech. In addition, Yusob (2018) states grammar is a challenging language skill since even experienced English lecturers may struggle to explain grammar to students. Therefore, English teachers must figure out how to persuade and motivate students to learn English by helping them to promote their problem-solving skills and creativity. One of the recent significant approaches to this aim is team teaching.
According to Gaytan (2010), the idea of team teaching is attributed to William Alexander, who is known as the father of the American middle school. His idea was to create teams of three to five middle school teachers, as a team, for large groups of students (75 to 150 students). He believed that team teaching leads to different educational and academic benefits, such as creating dynamic and communicative learning environments and a model for simplifying the teaching of critical thinking. Moreover, based on Calderón (1999) and Tajino and Tajino (2000), team teaching in language education creates chances for teachers to exchange ideas and cultural values, encouraging them to communicate with and learn from one another. Team teachers also have the chance to observe how their colleagues teach, reflect, examine their teaching practices, and make changes to become better teachers. In addition, according to Abell (2000), team teaching produces a very strong sense of collegiality that leads teaching from individualistic to cooperative teaching by breaking down the boundaries of privacy towards new kinds of teaching. Accordingly, Laughlin et al. (2011) believed that one of the most effective ways to keep a course alive and to introduce diversity in instruction is to use more than one teacher. Both teachers and learners benefit from team teaching because collaboration with a colleague boosts both teachers and learners and gets them thinking in new ways. It also can relieve some of the problems of teaching and of being just responsible for learning outcomes. Team teaching also endorses 9 collaboration (Duran et al., 2019) and can serve as professional development chances for co-teachers (Bacharach et al., 2007;Graziano & Navarrete, 2012;Hiesh & Nguyen, 2015).
According to Eisen (2000), team teaching has some advantages that let teachers (a) share power with a colleague to pave the way for sharing control with learners; (b) observe in advance what other professionals do in the classroom to contribute to modeling best practices; and (c) to gain insights while co-developing curriculum, planning assessment, and organizing material. Besides, Harris and Harvey (2000) reported on numerous advantages of team teaching for the learners, including (a) team teaching can open a learner's eyes to accept more than one idea and to work more collaboratively with others; (b) team teaching offers educational benefits such as increasing the student's level of understanding and retention; (c) two or more changing views help learners blur the black-and-white way of thinking and see many shades of gray.
Moreover, Robinson and Stabile (1995) stated that the collaboration that the students observe between team teachers acts as a model for teaching students positive teamwork skills and attitudes; and the benefits of this cooperative learning include more success, greater retention, better interpersonal skills, and progress in group work for both learners and teachers. Besides, Harris and Harvey (2000) believed the questions and comments that are done during discussions among team teachers let learners hear different opinions and perspectives, and learners can build off each other's contributions, respectfully challenging both the instructors and themselves. Finally, Marzocchi et al. (2021) described different benefits of team teaching, including the increased ability of the teachers to meet individual student's needs and increased engagement of learners in reflection.

Team Teaching
One of the new teaching approaches that have been used by teachers throughout the world in the educational system is team teaching. One of the first citations of the term team teaching is credited to Johnson and Lobb (1959). They believed that as a form of collaborative Continuing Professional Development (CPD) practice, team teaching refers to a pedagogical technique in which two or more instructors are assigned to teach a class simultaneously. Bess (2000) also states that team teacher's work together to plan goals and syllabi for the course, design individual lesson plans, share insights, and teach and evaluate students together. Moreover, according to Onyinye and Nkechi (2015), team teaching refers to bringing together two or more colleagues working together, but sometimes also working with professional and/or administrative colleagues -to plan, conduct, and assess the unit of study, including assessment, for the same group of students. Accordingly, Tsybulsky and Muchnik-Rozanov (2019) mention that team teaching shapes student teachers' professional identities.

Team-Teaching Models
As Cook (2004) states, various terms have been used to classify team teaching, including co-teaching, collaborative teaching, and cooperative teaching. In a broad sense, the term team/collaborative teaching shows the interaction of a team of teachers with a shared view toward active learning. In collaborative teaching, both teachers are in charge of instruction delivery, evaluation of students' achievements, and classroom administration. Accordingly, the literature introduces different types of team teaching.

One Teaches and One Observes
According to Cook (2004), in this approach, co-teachers decide what types of specific observational data should be gathered during the instruction and agree on a system for gathering the data. Then they analyze the information together. Based on Bacharach et al. (2010), in this way, one teacher is accountable for teaching while the other teacher observes data on students or teaching. Marzocchi et al. (2021) stated that the one teaches, one observe strategy allows one teacher to take the primary role in delivering instruction and implementation of the lesson for the class while the other teacher takes responsibility for observing and taking data on the class for further analysis and evaluation.

One Teaches, One Assists
In this approach, one teacher would keep the primary responsibility for teaching and the other would walk through the room providing aids to learners as needed (Cook, 2004). According to Bacharach et al. (2010) and Marzocchi et al. (2021), in this approach, one teacher undertakes the lead and the other teacher supports in a specific way in classroom management, class tasks, distribution of materials or responding to students' questions. For instance, an assistant can answer the learners` questions, especially when the main teacher teaches something new or when students are assigned to solve a problem (Smith, 2004). The interference between the assistance activity and the main teaching can be considered one of the disadvantages of this method.

Station Teaching
In this approach, teachers grouped students and content. Each teacher teaches the content to one group and then repeats it to another group. Thus, the class is divided in this approach, and learners change their stations. Some stations are led by co-teachers and some as independent stations (Bacharach et al., 2010;Marzocchi et al., 2021). Cook (2004) mentioned that some students need special help in most classes. In this approach, one teacher works with a small group that needs special help and the other work with the rest of the class. Bacharach et al. (2010) refer to this approach as differentiated teaching in which both teachers teach the same learning goal but use different approaches, such as visual versus kinesthetic. According to Marzocchi et al. (2021), alternative teaching allows each teacher to take a group of students and use an instructional approach that best fits the needs or learning style of the group. Cook (2004) defined the adjunct model of team teaching as teaching parallel courses in the same group of students. This model is a complement to a regular course. It means that the students sit in the regular course but have an adjunct class different from most students. This "adjunct" session is designed to help them perform alongside mainstream students.

Collaborative Interdisciplinary Team Teaching (CITT)
In Content and Language Integrated Learning (CLIL) the target of lessons is naturally a different field (such as history or biology), and instruction in such lessons is often shared between a content specialist and a language specialist (Pearce, 2019). Miyazaki International College used this form of team teaching for the first time. Using English as its primary medium of instruction, the college employs an unusual team-teaching practice called CITT in nearly all of its first-year and second-year classes (Gladman, 2015).

Native-Speaking EFL Teacher and Non-Native-Speaking EFL teacher.
In this approach, the class, as Pearce (2019) stated, may take the form of team-taught classes conducted by a Native-English-Speaking Teacher (or NEST, typically of a different nationality to the other classroom participants) and a local, Non-Native-English-Speaking Teacher (or NNEST, who usually shares a cultural background with the student).

Supplemental Teaching
As Bacharach et al. (2010) believe, one teacher undertakes the main instructional role and the second teacher works individually with an intentionally selected small group of learners who are still motivated to learn the content or are ready to learn some other supplementary materials. Anderson and Speck (1998) provided the method of team teaching in their research for a five-week summer session at the Memphis Urban Writing Institute. They found that four variables of team teaching can influence students' learning:

Related Studies
1. Team teachers' compatibility (results showed that while it is acceptable and desirable for team members to have different teaching styles, they must be well-matched, committed, and concise about the class visions). 2. Team teachers' expertise (results showed that student learning is improved by instructors' multiple viewpoints and sharing of different teaching experiences). 3. Team teachers' gender (results showed that learners were mixed in their opinion about gender impacting their learning in a team-teaching environment. They believed having each gender represented in the classroom was a positive experience. Learners might be connected to one teacher more than the other, and student's needs can be more eagerly met when there are two teachers). 4. Classroom environment (results showed that team teaching is an effective way to facilitate the creation of a cooperative classroom environment). Moote (2003) interviewed English teachers in a team teaching environment in Japan's public schools. Ten teachers participated in this research project. Of these, five are Japanese Teachers of English and five are Non-Japanese Native-speaking English Teachers. The main purpose of these interviews was to find out how team teachers consider what they do. The study results showed that those teachers who prefer both forms of teaching believed that the solo-taught lessons provide a chance to discover the students` needs. On the other hand, those who favor team teaching believe that teachers and students benefit from being exposed to diverse learning styles. They may also receive feedback and support on their teaching and obtain advice about their questions concerning English. Stewart and Perry (2005) explored how interdisciplinary interaction between language and content authorities might be considered a possible model for teacher development. For this purpose, 14 practicing team teachers were interviewed over two years at an English college in Japan. The interviews were all recorded on videotape and were transcribed for later analysis. In this study, courses are team-taught by one TESOL expert and one content expert in the humanities or social sciences. The results showed that students benefit from an effective partnership because the team members offer the students two perspectives on key issues and concepts in the course. They also benefit from the interaction of a successful partnership. The results also showed that the team-teaching process helps teachers to become more creative and insightful. Carless and Walker (2006) studied the collaboration between Native-speaking English Teachers (NETs) and Local English Teachers (LETs) in Hong Kong secondary schools. The study emphasized how native and non-native teachers worked together and how their collaboration impacted themselves and their students. The paper illustrated that collaboration between NETs and LETs is a challenging task but, when handled thoughtfully, can display the strengths of each party and minimize their weaknesses. Tsai (2007), following the design of qualitative case studies, tried to find out the team-teaching experiences of foreign and local English teachers in Taiwanese elementary schools and team teachers' ongoing growth in this context. Data were gathered using observations, interviews, and document analysis within six months. The study showed that each team developed different team-teaching styles and various collegial relationships based on the different mixtures of the team teachers. However, despite these differences, team teaching was chiefly revealed as the Taiwanese teachers' educational responsibilities and duties and  providing consultation. Furthermore, their collegial communications were influenced by different factors such as age, gender, personality, language, professional respect, assumptions about teaching and team teaching, communication styles, workload and scheduling, administrative roles of the teachers, and amount of teacher training. The findings also suggest that the team teachers benefited from the team-teaching experience in six aspects: language knowledge and skills, knowledge of culture, teaching skills, understanding of students and schooling, development of partnerships, and development of professional identity.
Gurgur and Uzuner (2011) stated a need for evidence-based research projects regarding supporting students with the coteaching method. They worked on one regular teacher and the researcher as a special education teacher in action research. This study was done in a second-grade elementary classroom in a school located in a low-income district in Ankara, Turkey. The class consists of 35 learners (22 girls and 13 boys). Two of these students (one girl and one boy) were with special educational needs. The learners had been together with the class teacher for two years. Following the article's aims, it was decided to study the team teaching and station teaching models. Data was collected through a checklist, documents (lesson plans, students' products), researcher journals, recordings of co-planning, and reflection meetings and instructions. The results showed that for providing effective co-teaching, the class settings should be arranged and supported with additional teaching materials, and the number of students in classes should be reduced for successful team teaching. It is also proposed that the co-teaching teachers should be innovative, volunteer, and adequately experienced in the areas of planning and evaluation. Bardaglio et al. (2015) used team games to boost coordinative motor skills in primary school kids. They also aimed to find out whether the program is or is not more effective when they used team teaching with two, instead of one, teachers. The participants were 205 children in the third grade of primary schools in Italy. Three public primary schools were chosen randomly among all the primary schools with similar intermediate settings regarding the parents' socio-economic levels and the surrounding ecological environment. In each school, one class was assigned to the experimental group with one instructor, one to the experimental group with two teachers, and one to the control group taught by their regular teacher. The six teachers were all women. The findings showed that the program improved the children's coordinative motor skills in team games. Correspondingly, their coordinative motor skills increased more in the experimental conditions with two teachers than in the group with only one teacher. Jenkins and Crawford (2016) investigated the application of a blended learning process underpinned by team-teaching strategies. The study focused on ascertaining the impact of implementing team teaching. It blended classroom learning and how these two approaches could be combined to positively affect the pre-service teachers' learning. The findings concluded that team teaching had a positive impact overall, while blended learning positively impacted most participants. For the researchers, these findings substantiated the benefits of combining the blended-learning and team-teaching approaches in the preservice classroom but also suggested that certain aspects needed to be refined and modeled. Baeten et al. (2018) study team teaching in their article. They focus on the assistant teaching model, in which the studentteacher assists the mentor during teaching. They examine which assisting activities student teachers prefer, how student teachers and mentors experience these activities and the situations that they can predict for implementation. Participants were three men and 15 women student teachers with different teaching subjects such as Biology (n = 2), Chemistry (n = 2), Economics (n = 2), French (n = 5), Behavioral Sciences (n = 3), Dutch (n = 2), and Mathematics (n = 2). Results showed that mentors prefer implementing the assistant teaching model during lessons where pupils work individually or in small groups. During these activities, the student teachers function as a guide so that additional support can be provided to the pupils. King (2018) worked on how co-teachers can jointly accomplish the initiation and feedback work in Initiation-Response-Feedback (IRF) sequences. Two team teachers (doctoral students) and their 24 graduate students, including the researcher, participated in this study. Two class sessions covering nearly three hours were videorecorded during the fifth and sixth weeks of the semester. Two video cameras were arranged on either side of the classroom to capture as much of the teacher's verbal and nonverbal behavior as possible. The first section describes two instances of joint initiation, wherein the co-teachers work jointly to complete the initiation work in an IRF sequence. The subsequent section describes three examples of joint feedback, wherein the coteachers jointly offer the feedback in IRF sequences. The practice of joint initiation reveals two slightly different perspectives between the teachers about what the students are ready to do with the new material. While joint feedback can work to make one individual's evaluation potentially more visible, the practice can also enable co-teachers to manage competing voices and evaluate multiple students at once. The results reveal that co-teachers with equal roles can jointly occupy not only the same IRF sequence but also the same sequence component. Rickard and Walsh (2019) work on a team-teaching pilot project in the education department for student teachers and their cooperating teachers. The study aims to reevaluate the approach to teacher education, study the team-teaching process, emphasize its affecting dimension, and advance collaborative practices in education. The findings from the project data are outlined under five key themes: prior experiences and motivation to be involved; perceived benefits of team teaching for teachers; perceived benefits of team teaching for pupils; the importance of relationships; and constraints to practicing team teaching. Despite the lack of training, however, 73% of the cohort noted that team teaching was practiced in their schools, with 38% (eight respondents) saying that team teaching occurred almost daily. The next highest number of respondents (24% or five respondents) reported an occurrence of team teaching 'about once a month.' When asked about their involvement in this team teaching in their schools, four indicated that they were frequently or quite often involved, while all the others indicated that they would engage in it, albeit less frequently.
Wong and Nguyen (2019) aim to discover the students' and teachers' attitudes toward team teaching using a mixedmethod research design and a reflective teaching approach. First, the leader teacher presented how a transition word is used by making a sentence in Vietnamese and explaining how a Vietnamese transition word links ideas. Then, the leader teacher gives time to students to translate the statements. This task aimed to train students to reason and think in English. During this time, the threeteam teachers circulated the whole class to support the students if requested. The whole class was invited to read their translations when the time was up. While the students were doing this task, the three-team teachers circulated among the whole class, supporting the students if requested. The team teachers switched the circulated places so that all the students would have the opportunity to work with all the team teachers. The key findings were (a) team teaching in English writing classes was valued by the students who got many profits from it; and by the team teachers who had the opportunity to avoid academic loneliness and to reinforce the students' belief in team teaching; and (b) most other teachers, though admitting the profits of team teaching, were not satisfied with using team teaching in their English writing class. The findings also show that 80% of students agreed that the teamtaught writing class was effective, enjoyable, and appropriate for their English level. Finally, teachers admitted that team teaching aided in developing mutual relationships among team teachers.
Tsybulsky and Muchnik-Rozanov (2019) studied the projectbased team-teaching method in elementary schools inviting 17 student teachers. The study focused on student teachers' experiences regarding quality and content. The student teachers worked in teams (which they formed based on their own choice). The majority of the team-teaching experiences designated by the student teachers were related to social communication with others. Regarding the quality of the experiences, most participants (5/6 teams) reported having positive experiences of valuable collaboration. Findings indicated that during team teaching, the student teachers underwent a process of four qualitatively different experiential stages: (a) The organizational stagecreating the groundwork for team teaching; (b) The planning stage -setting up the project; (c) The performance stage -teaching project-based lessons; and (d) The conclusion stage -completing the process and follow up. One of the student-teacher teams expressed dissatisfaction with the teamwork and reported a negative emotional response to the team-teaching framework.
Canaran and Mirici (2020) work on team teaching as an inservice professional development program that draws on the principles of effective continuous professional development (CPD) practices. The team-teaching model is practiced in phases, including research, collaboration, and reflection, focusing on learner-centered instruction. The study invited three non-native EFL teachers as the study's participants. In the study context, all English teachers had a weekly teaching load of 20 hours. Apart from teaching, they were required to perform academic and administrative duties, such as monitoring and grading exams, holding office hours with students, organizing extracurricular activities, and translating written texts. The data for the study were obtained from semi-structured interviews and archival records. The results showed that the teachers' reflections centered on what they did and learned through the phases of team teaching, what they believed about the model, and how they felt from the beginning to the end of the teaching process. Besides, the findings showed a gradual move from negative to positive views on team teaching by the end of the study. The results also showed that despite some hardships, such as adjusting to teamwork and finding the energy and time needed for collaborative planning and teaching, this new team teaching model could enhance teachers` awareness, trigger reflection, encourage thinking about student needs, and improve research skills.
Mursidin and Jusmaniar (2020) work on the implementation and the benefits of the English team teaching using an observation checklist and interview. In this case, two English teachers, one man and one woman, are the subject of the research. In collecting data, the researcher used interviews and observation. The results of the observation checklist showed that all the team teachers shared all the activities in team teaching, from planning, implementation, evaluation, and responsibilities in implementing team teaching. The interview results showed that the team teachers discussed and worked together in every phase of the teaching and learning process. The researcher also found that some problems were found by the team teachers implementing team teaching, but they solved the problems through good communication with each other. The team teachers have different roles and responsibilities in implementing team teaching, and the English teachers felt that team teaching is an effective and efficient method in the teaching process. Simons et al. (2020) explore two team-teaching models, parallel and sequential teaching, by examining the student teachers' perspectives. Quantitative (survey) and qualitative (self-report) methods were used to investigate their attitudes toward both models and collaboration, advantages and disadvantages, and the conditions for implementation they consider critical. Fourteen student teachers participated in the study. They all had bachelor's and master's degrees and were between 22 and 36 years old. In parallel teaching, they divided the class so that each student taught a subgroup in a different classroom. In sequential teaching, teachers alternatively divide the content between teachings within a lesson. Later, student teachers reflected together, and the mentor observed and gave feedback after each lesson. Results showed that collaboration in sequential teaching is significantly higher for teaching and peer reflection. In addition, an important overlap between the actual and the desired collaboration level was observed for sequential teaching. For parallel teaching, however, student teachers were quite satisfied with the collaboration level for lesson preparation but would prefer more intense collaboration during teaching and for peer and mentor reflection. Muza (2021) used a pre-test and post-test quasi-experimental design to determine the effects of the team-teaching approach on academic performance in Nigeria. The study used self-constructed open and closed-ended questionnaires as data collection instruments. With the help of a research assistant, the researcher administered a pre-test to both the controlled and experimental groups. The study showed the experimental group was significantly different from the control group (the single-teacher approach). Besides, no significant difference was found between the mean scores of boys and girls students taught using the teamteaching approach (Experimental group). Potter et al. (2021) surveyed students' satisfaction with the two key elements: team teaching and an interdisciplinary curriculum. Eighty-five participants, 74 current and 11 pass-out graduate students, participated in the study. The results showed that depending on the type of team-teaching (co-teaching when both instructors taught concurrently, alternate teaching when the instructors interchanged their roles or a panel of three or more instructors), there were no significant differences between teamteaching and traditionally taught classes. However, there were differences in student attitudes toward the type of team teaching. Students preferred the co-teaching model to the alternate and panel models. Shaw (2021) explores the experiences of educators who teamtaught graduate-level students. Data were gathered in the form of one-on-one interviews. This study identified that educators gain professional and personal from social interactions with their peers. Accordingly, Marzocchi et al. (2021) report on a semester-long coteaching investigation in which three teachers enacted a coplan/co-teach model in the context of a mathematics content course for future elementary teachers. The team-planning method was involved pre-splitting the lesson among the team teachers so that each teacher focused on the part of the lesson content. The findings showed that with co-teaching strategies such as Parallel or Station Teaching, it is predetermined which [pre-service teachers] are assigned to which teacher. However, when implementing Team Teaching or One Teach strategies, both teachers have the whole class in front and it is unclear who should check in with which groups. When dividing a lesson by task, each co-teacher focuses on half the tasks and uses this to guide her rotation around the classroom. Each co-teacher rotates to monitor student thinking on their tasks, asking follow-up questions and assessing student understanding. Doing so helps to eliminate redundancies of co-teacher questioning because each co-teacher targets distinctly different tasks. Another benefit is that each coteacher can achieve a greater level of questioning and learn about student reasoning when focusing on smaller tasks. By dividing the lesson content, they knew their goals before interacting with preservice teachers and consequently knew what to look for while monitoring their work. It is also reported that co-planned lesson division encouraged co-teachers to visit groups more fairly, maximize interactions with pre-service teachers by eliminating repeated questions, and prepare a co-plan/co-teach model they likely have not experienced.

Research Questions
The researchers of the current study posed the following research questions by considering the "one teach, one assist" model of team teaching: 1. Does online team teaching significantly affect Iranian EFL learners' grammar improvement? 2. Is there any significant difference between Iranian EFL learners' grammar improvement regarding their gender?

Methodology Participants
Fifty intermediate students studying the English language as their foreign language participated in this study. These students are placed according to their level by the institute into two classes. Thus, the researcher has two 25-student intact groups (experimental and control), leading the research into a quasiexperimental design. Students' age ranged between 11 to 16 (M = 13, SD = 2.1). Twenty percent of respondents to the test in the control group and 32% in the experimental group were boys, and 80% in the control group and 68% in the experimental group were girls. The classes were held on the Adobe Connect platform. The "one teach, one assist" model was selected as the study's teamteaching method.

Materials and Instruments
To find out the effect of the study's treatment, a 20-item multiple-choice grammar test (developed and validated by the institute based on the students' coursebook) was used as both the pre-test and post-test. The test has alpha reliability of .79 and was administered online using Google Forms on a 20-minute time limit.

Procedure
There were two classes in this study. One was a team-teaching class (Experimental group) which included the main teacher (the researcher herself) and an assistant, and the control group class. There were ten sessions for both classes and grammar issues such as the simple present, present continuous, past simple, past continuous, future tense, present perfect, past perfect, future perfect, and used to were covered. Murphy's course book was English grammar in use intermediate (2012). The class ran on the Adobe Connect platform and the contents were provided using PowerPoint. Therefore, teachers and learners were required to attend the class with a PC or laptop and have access to a camera, a microphone, and an Internet connection. Every session the class started with a warm greeting from the assistant, called the roll, reviewed the previous session, and then the main teacher started to teach the topic and provided learners with some examples. Next, the assistant returned to answer the question, provided more examples, and did the activity. At the end of each session, the assistant gave learners the homework and they had to send it to him. Finally, paired and independent-sample t-tests were used to determine any difference between the control and experimental groups and to find any significant differences between boys and girls students' structural abilities.

Results
At the beginning of the study, a pre-test in terms of grammar improvement was taken from Iranian EFL learners in both control and experimental groups. The results showed that the pre-tests mean scores of the participants in the experimental and control groups were 11.48 and 11.00, respectively (Table 1). Therefore, it seems there was not a great difference between the control and experimental groups in their grammar improvement at the beginning of the study. To prove this statistically, an independent samples t-test was run (Table 2). Note. N = 50. SEM = standard error mean.
An independent samples t-test was run to compare the mean scores of the two groups to see if there was any significant difference between the groups regarding their grammar pre-test scores ( Table 2). The result suggests that the two groups were homogeneous in terms of their grammar improvement and no significant difference was observed between groups in the pre-test (t (48) = -.89, α = .05, p = .37).
In order to find out which group has improved more significantly from the pre-test to the post-test, their post-test scores were compared using an independent samples t-test (Table 3 & 4). .60 Note. MD = mean difference; SEM = standard error mean; CI = confidence intervals; LL = lower limit; UL = upper limit. Table 3 indicates, the post-test mean scores of the participants in the experimental group are 18.32 and 17.16 in the control group. Accordingly, as shown in Table 4, there was a statistically significant difference between the experimental and control groups (t (48) = -2.58, p < .05) in their performance in the post-test. Therefore, it can be concluded that treatment in the experimental group was effective, and online team teaching significantly affected the Iranian EFL learners' grammar improvement.  Moreover, to examine any significant difference between Iranian EFL learners' grammar improvement regarding their gender on their post-test, a comparison of the means of two groups was performed by an independent sample t-test (Tables 5 & 6). The results revealed that the grammar improvement variable totally in the post-test had a significance level more than the SE = .05, reflecting that the mean of men and women did not differ significantly in this variable.  1.03 Note. MD = mean difference; SEM = standard error mean; CI = confidence intervals; LL = lower limit; UL = upper limit.

Discussion
The results of this study indicated that team teaching significantly affects Iranian EFL learners' grammar. In the same vein, Mursidin and Jusmaniar (2020), who works on the implementation and the benefits of the English team teaching using an observation checklist and interview, concluded that team teaching is an effective and efficient method in the teaching process. Moreover, Muza (2021) used a pre-test and post-test quasi-experimental design to determine the effects of the team-teaching approach on students' academic performance and reported that the experimental group was significantly different from the control group (the single-teacher approach). Shaw (2021) also stated that team teaching has a positive effect on learners learning and it can persuade them to be more active and encourage them to study more to get better feedback from both teachers.
The current study's results also showed no significant difference between learners' grammar scores and the results of team teaching concerning their gender. This is in line with the study of Bardaglio et al. (2015) showed that students progressed more in the experimental conditions with two teachers than in the group with only one teacher. However, this success was the same for both boys and girls. Besides, Muza (2021) found no significant difference between the mean scores of boy and girl students taught using the team-teaching approach (Experimental group).

Conclusion
In this study, the researcher tried to motivate and make progress in learning grammar for Iranian language learners through team teaching. Twenty-five learners, boys and girls, were selected for each group (Experimental and control). The results indicated that the study's treatment (implementing a team-teaching approach) significantly affected the experimental group students` grammar progress. The results also showed that the cooperation between the teacher and the assistant had been done properly and satisfied the learners. Furthermore, the advantages of team teaching, as learners mentioned, indicate that learners are interested in joining the team-teaching class and benefit from different teaching methods. Besides, the cooperation between the instructors is exciting for them and they can be in touch with both teachers.
Accordingly, this method can be useful for English language institutes, making their classes more attractive with more tension. It can be considered a beneficial technique for the instructors to learn from their colleagues and share their responsibilities and plans for managing the team-teaching classes. Besides, familiarity with online team-teaching techniques may help teachers to overcome the exhaustion of grammar lessons and persuade learners to be more engaged. They can learn how to share their ideas with their colleagues and divide their class responsibilities by focusing on one part of the teaching materials. In addition, team teaching can be effective for researchers and language school managers or supervisors because they can use the results of this study to help their teachers to be familiar with and implement team-teaching strategies.

Limitations
This study has some limitations in using the internet due to the low quality of the internet. As the institute held the two classes, the researchers could not randomize the participants. Therefore, further research can focus on true experimental research design by randomly selecting and assigning participants to experimental and control groups. In addition, because of the CoronaVirus pandemic, the researchers decided to hold the classes in the online form, so they performed online team-teaching instead of face-to-face team teaching. Besides, other researchers can select other English skills and components as their focus.