Research about teaching competencies in the context of inclusion focuses so far attitudes and does not take adequate account of professional knowledge. This paper investigates what kind of knowledge is relevant from the view of teachers in practice to handle inclusion in schools. Interviews of 53 teachers of different types of school were analysed qualitatively with a literature based category system. First, the perspective of all interviewed teachers is presented. It follows an analysis, which regards the type of school and the level of school development. Our results show that teachers use the categories, which are abstracted from the research literature. These categories need to be supplemented by inductive categories. There is a difference between the types of school, and a relation between school context and professional development of individual teachers. This could be discussed as a specific indication for teacher trainings, which aim to foster inclusive competencies.