The present article reports on a case study into the influence and impact of action research carried out by teachers in a special school. The action research was an important component of the two-year, post-initial, in-service course in special educational needs, provided by Fontys University of Applied Sciences, Department of Inclusive and Special Education. From the outset the case study was based on the premise that action research can be seen as a strategy for teacher leadership. Not only was it expected to help teachers to get to grips with their own work in the classroom, it was anticipated that their action research would also have an impact on the work of others in the school. We found that this was indeed the case, provided certain conditions were met. (Contains 2 notes and 2 figures.)