This thesis aims to contribute to knowledge about how teachers can develop their practice to enable students with intellectual disability (ID) and autism to participate in education. Pragmatism, situated learning, and variation theory have been guiding the studies. The research program follows an iterative design with an exploratory sequential design. The initial phase synthesized findings from practice-based research in the educational context of children with ID and co-occurring autism. In the next step, an intervention using Lesson Study, inspired by identified gaps in the research, targeting teachers' professional development and students' learning, was explored through quantitative and qualitative analyses of pre-and post-test data. After the initial examination, the intervention was adjusted and implemented in compulsory schooling for pupils with learning disabilities (CSPLD), for pupils with ID and autism. The main research question was: What, in a professional development program, contributes to enhancing teachers' abilities to develop teaching to increase educational participation for pupils with ID and autism?The narrative synthesis discerned six factors of importance to developing teaching practices in the Swedish CSPLD and thereby promoting contextualized inclusion for pupils with ID and autism. Namely, a. the inportance of collaborative work, b. focus on the pupils' participation in learning situations, c. distance to own teaching by video-based reflections, d. structured observations, e. analyses of how the design of lessons affects pupils' learning, f. changed focus from pupils' behavior to teaching and learning, and more generally, continuity regarding professional development over time. In conclusion, to gain further knowledge of teaching and learning in the context of CSPLD and achieve sustainability in the community where teachers share knowledge and curiosity about teaching and learning, Lesson Study is recomended as part of the SEND teacher commitment.