The authors trace the development of the King's Formative Assessment Programme from its origins in diagnostic testing in the 1970s, through the graded assessment movement in the 1980s, to the present day. In doing so, they discuss the practical issues involved in reviewing research and outline the strategies that were used to try to communicate the findings to as wide an audience as possible (including policy-makers and practitioners as well as academics). They describe how they worked with teachers to develop formative practice in classrooms, and discuss the impact that this work has had on practice and policy. Finally, they speculate about some of the reasons for this impact, and make suggestions for how the impact of educational research on policy and practice might be improved.