Few longitudinal, mixed methods studies focusing on teachers' views of inclusive teaching have been conducted in primary schools. This article draws attention to a Swedish in-service (K-5) school improvement research project, aiming to contribute to a school's development toward improved inclusive education, where teachers' experiences were analysed, using mixed methods, at the beginning and at the end of the project. Data consisted of items extracted from the TALIS 2013 survey questionnaire and semi-structured interviews. The observed change between the first- and second-year surveys and interviews emphasised a connection between teachers' confidence, self-efficiency, collaborative professional development, and successful school development. What signified the development of inclusive education was moving away from categorising the needs of individuals with learning disabilities towards focusing on active teaching, mutual engagement, and content knowledge for all students.