In response to international and national policies towards the inclusion movement, co-teaching between general and special educators has evolved as one approach to the education of students with and without disabilities in the general education classroom (Friend et al., 2010; Strogilos et al., 2017).  Co-teaching is defined when special and general educators plan and implement instruction to a diverse group of learners, including those with disabilities, in general education classrooms (Friend, 2008).

Research on co-teaching has extensively grown in the last decades. Researchers have examined co-teaching to depict its nature, process, and impact.  This examination includes several considerations such as co-teaching as a special education delivery approach (Friend et al., 2010) or as a provision that offers the best of both special and general education worlds (Villa et al., 2008). It also includes co-teaching as an approach which has some evidence for increasing the academic achievement of students with disabilities (King-Sears et al., 2021) or all students (Bottge et al., 2015). As such, co-teaching has been conceptualized and researched across different educational contexts and policies, albeit how different they might be in their approach to the education and inclusion of students with disabilities. Because the relationship between co-teaching and inclusion varies (Strogilos et al., 2017; Villa et al., 2008), in this paper we consider co-teaching as one of several approaches in which educators include students who have disabilities with their same-age peers for some or all of the school day. As such, co-teaching can enhance the physical and instructional participation of all students included in the co-taught classroom, especially those with disabilities. 

Cook and Friend (1995) proposed several co-teaching models: two educators share the planning and delivering of instruction by each leading instruction (team teaching), dividing students among the two teachers (parallel or alternative teaching) or dividing students in stations (station teaching), and one teacher leading while the other primarily assists or observes (one-teach, one-assist or observe or circulate). Nevin et al. (2008) noted that both educators “are responsible for instructional planning and delivery, assessment of student achievement, and classroom management” (p. 284) echoing Thousand et al.’s (2006) stance that when educators collaborate on planning and teaching, they can be more responsive to the needs of students. Despite co-teaching’s intuitive appeal (e.g., two heads are better than one) and its popularity, research on co-teaching has identified several challenges (Scruggs et al., 2007). There is only one published systematic meta-synthesis of qualitative research on co-teaching by Scruggs et al. (2007) in which they reviewed 32 studies published till 2005. Overall, Scruggs et al. found that little parity existed between co-teachers with unclear roles and responsibilities and limited co-planning time. Scruggs et al. concluded that effective co-teaching could be achieved with more focus on co-teachers’ training and use of research-based practices, and administrative support that promoted co-teachers’ time to plan and determine roles and responsibilities. Advances on co-teaching since 2005, are difficult to discern without an attempt to synthesise them. Thus, there is a need for an updated systematic examination of qualitative research on co-teaching.

The main aim of the present meta-synthesis is to describe the practice of co-teaching and its impact to students and teachers by connecting and interpreting findings from stand-alone qualitative studies to offer new interpretations and insights (Nye et al, 2016). We address three research questions:

1. How do researchers conceptualize co-teaching in designing their research studies?
2. What are the features that influence teachers’ practice in co-taught classrooms?
3. How do co-teachers and researchers describe the impact of co-teaching on co-teachers’ learning as well as on students’ with and without disabilities academic and social progress?

We used a descriptive-interpretative approach as our main epistemological framework to generate new theoretical/conceptual models to identify gaps in research, and to generate new questions from the meta-synthesis (Timulak, 2009). As such, the included studies were described, synthesized, and critically interpreted. To identify potential studies, we undertook computerised searches in EBSCO, ERIC, Academic Search Complete, OmniFile Full Text Select, and PsycINFO and hand-search strategies. We used the search terms of “co-teaching,” “coteach,*” “co-operative teaching,” “cooperative teaching,” “collaborative teaching,” and “team teaching” to search related “titles,” “abstracts,” and “keywords.” Two authors independently examined the records for relevancy. Titles, abstracts, and full texts were reviewed to determine eligibility. The inter-rater reliability for determining eligible studies was 90%. A third author scrutinised discrepancies to reach consensus at 100% inter-rater reliability. We applied the following selection criteria to identify eligible studies: (a) original qualitative research studies or mixed-methods with a clear qualitative data collection part (only the qualitative part of these studies was included in the synthesis); (b) published in peer-reviewed journal; (c) co-teachers were general and special educators; (c) K-12 grades; (d) in English; and (f) when other participants in the study (e.g., students), data from the co-teachers were disaggregated. Exclusion criteria were: (a) research focusing on inclusion but not on co-teaching; (b) Educators were part of a larger team working together but not co-teaching; (c) participants were administrators or pre-service teachers; and (e) surveys with open-ended questions on co-teaching. After excluding duplicates, ineligible, and irrelevant articles, we reviewed the full text of 110 articles from which 47 included in the meta-synthesis because they met all our inclusion criteria. Each eligible study was reviewed for quality using the CASP tool (CASP, 2018). Although eligible studies varied in their approach to data collection and quality, we retained all of them because we considered that the different knowledge each study produced was important for the synthesis. We conducted a two-staged analysis. First, we read all studies in order to extract in a Word document the fundamental characteristics of each study (e.g., research questions, summary of findings) called a “research report.” Second, we used NVivo 12 to complete thematic analysis as proposed by Braun and Clarke (2006): generate initial codes, search for themes, review themes, define and name themes, and write the final report. We focused on the primary participants’ and researchers’ accounts to identify repeated patterns of meaning, exceptional cases, and meaningful interpretations of findings.

In line with our first research question, we identified three conceptual frameworks that the authors used to research co-teaching. The first focuses on how co-teachers learn to co-teach, the second describes the practicalities of co-teaching, and the third the content of teaching and forms of instruction that co-teachers use. To answer the second research question, we identified a number of features such as co-teachers’ relationship and how they learn from each other; their training needs and the lack of planning time; the importance of volunteerism and co-teachers’ voice; and how specific contextual features (e.g., exams) influence the selection of models and the curriculum, and even the use or absence of accommodations and modifications. We found that the above features influence co-teaching and that co-teachers and researchers talk positively about its benefits on teachers’ learning and students’ academic and social progress which was the focus of the third research question. Overall, co-teaching has progressed from an approach to service students with disabilities in the general classroom to an approach that can positively enhance all students’ and teachers’ learning. Since the physical and instructional inclusion of students with disabilities in general schools is an ongoing process, the approaches which can contribute towards this, such as co-teaching, should be also considered as developing themselves. Based on what we learned from this meta-synthesis, we argue that the education of students with disabilities in the general classroom through co-teaching cannot be the main focus for its future development. Co-teaching needs to be considered by policy makers, researchers and practitioners as a context of learning for teachers and a dynamic framework with the potential to develop effective instruction for all students included in the co-taught classroom. Research on co-teaching should be conceptualized, planned, and implemented with all the students included in the co-taught classrooms in mind.

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