Collaboration and co-teaching between regular and special education teachers are widely regarded as key drivers of school development and as essential prerequisites for the successful implementation of inclusive education (Friend et al., 2010; Sundqvist, 2021). Despite this robust normative consensus, collaboration often remains loosely conceptualized and weakly institutionalized in everyday school practice (Vangrieken et al., 2015). Empirical findings consistently indicate that intensive and reciprocal forms of collaboration are still the exception rather than the rule, with many collaborative arrangements characterized by limited coordination or a pronounced division of labor (Pozas & Letzel-Alt, 2023).

Despite the extensive research that has been conducted on teacher collaboration, important conceptual and empirical gaps remain. Existing research has tended to focus on either the conditions under which collaboration takes place (e.g. Vangrieken et al., 2015) or on the processes through which it unfolds (e.g. Pozas & Letzel-Alt, 2023). However, the interrelation remains insufficiently understood (Gourvennec et al., 2024; Jurkowski & Müller, 2018; Strogilos et al., 2022). Furthermore, teachers’ professional beliefs about successful collaboration have rarely been systematically linked to both collaborative conditions and processes. This is despite the theoretical assumption that such beliefs play a central role in guiding professional action (Ajzen, 1991).

Addressing these gaps, this study investigates the interplay between collaborative conditions, collaborative processes, and teachers’ beliefs about successful collaboration in inclusive school contexts. The following research question is proposed: what types of collaboration can be identified based on collaborative conditions, collaborative processes, and their convergence with teachers’ beliefs about successful collaboration? The objective of this study is to develop a typology grounded in empirical evidence, with the aim of providing a novel perspective on the subject.

In the theoretical framework on collaborative conditions conceptualizes collaboration as a multidimensional and multi-level phenomenon embedded within personal, interpersonal, organizational, and structural contexts (Lütje-Klose & Urban, 2014; Vangrieken et al., 2015). The analysis systematically identifies facilitating and hindering conditions. The collaborative processes are analyzed with a focus on their intensity. Drawing on established models of teacher collaboration (Gräsel et al., 2006; Marvin, 1990; Little, 1990), collaborative practices are categorized as either fragmentary or intensive. Teachers’ beliefs about successful collaboration constitute a third central analytical dimension. These beliefs are understood as relatively stable professional orientations that shape perception, interpretation, and action (Vries et al., 2014). The present study introduces the concept of convergence as a key analytical lens to examine if the beliefs held by the co-teachers align with, or diverge from, the collaborative conditions and processes that characterize their professional practice.

Integrating collaborative conditions, collaborative processes, and co-teachers’ beliefs into a single analytical framework is a significant contribution of this study, as it facilitates a more comprehensive theoretical understanding of collaboration in inclusive education. Concurrently, the empirically derived typology offers practice-relevant insights for the effective support and further development of collaborative practices in school contexts.

In order to address the overarching research question, this study adopts a multiple case study design embedded in a parallel mixed-methods approach, with the aim of developing an empirically grounded typology of teacher collaboration. The case studies are based on observations, questionnaire data, and interviews, enabling an in-depth exploration of complex social and interactional processes in real-life school contexts (Yin, 2018). The utilization of multiple cases enables both within-case analyses and cross-case comparisons, thereby facilitating the identification of patterns and differences. This, in turn, contributes to the development of theory beyond the limitations of single-case findings. Empirical data are analyzed following the typological approach proposed by Kelle and Kluge (2010), which provides a systematic framework for integrating heterogeneous data and comparing cases. The analysis is guided by three core dimensions: The first condition is that of case-specific collaborative conditions at individual, interpersonal, and organizational levels. The second condition is that of collaborative processes between co-teachers, with a focus on interactional intensity. The third condition is that of alignment or divergence between teachers' professional beliefs and observed conditions and processes. Integrating qualitative and quantitative data across these dimensions, the study develops an empirically grounded typology of collaboration, offering a nuanced understanding of collaborative practices in inclusive school contexts.

This study makes a substantial contribution to the extant research on interprofessional collaboration in inclusive education by developing an empirically grounded, multidimensional typology that integrates collaborative conditions, collaborative processes, and teachers' professional beliefs. In-depth case analyses reveal three distinct types of collaboration. Type 1 is characterized by intensive collaborative processes within facilitating conditions that align with teachers' beliefs, reflecting a mutually reinforcing relationship between structural arrangements, interactional practices, and professional orientations. Type 2a combines fragmentary collaboration with constraining conditions but still shows convergence with teachers' beliefs, highlighting productive tension between normative models and professional orientations. Type 2b is characterized by the presence of fragmentary collaboration under constraining conditions, accompanied by a divergence between practices and beliefs, revealing tensions between professional ideals and enacted reality. The findings demonstrate that collaboration in inclusive schools cannot be understood through processes alone. Instead, it is essential to examine the interplay of conditions, practices, and beliefs. Despite the typology's analytical transferability, it offers substantial heuristic value for pedagogical practice. This is because it enables teachers to reflect on their collaborative processes, evaluate alignment with their professional beliefs, and identify avenues for improvement. The study concludes by highlighting its limitations and outlining directions for future research on the dynamic relationships among beliefs, conditions, and collaborative practice.

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