This paper reports on a collaborative research study between three secondary teachers and two university researchers, initiated by the teachers, into the practice and impacts of assessment for learning in science, geography and history classes. The research provides insights into how teachers and researchers can collaborate to develop a research and practice agenda. The study illustrates the need for a dynamic interconnection between the personal, micro or school-related level and the macro or policy level factors. The findings highlight the importance of external support, shared teacher knowledge and beliefs, professional experimentation, and shared reflection on student responses to classroom innovations.