This study used video feedback in a collaborative development study to help improve teachers' perceptions of the learning needs of students with autism spectrum disorders (ASD) and intellectual disabilities (ID) and enhance their active participation in the classroom. Crucially, teachers need the necessary skills to discern students' subtle communications, as students with ASD and co-occurring ID may have reduced or non-existent verbal language and may express their needs mainly through behaviours. The first author video recorded ten classroom lessons and collaborated with three teachers to discuss the recordings in six meetings over the course of one semester. The data used for the analysis was taken from the first (February) and last (June) collaborative meetings of the semester. The results show how collaborative video feedback can influence teachers' judgements about students' learning and further their professional development; the subtle signals that students use to communicate become more visible when the video recordings are viewed multiple times. The collaborative discussions facilitated the teachers' understanding of students' behaviours and actions. In addition, the teachers' focus shifted from identifying general aspects of their students' behaviours to their skills and knowledge.