Knowledge exchange interventions are an important driver of research impact. This study examines 5 years of intensive knowledge-exchange 'reform labs' in the field of education policy. Using qualitative analysis and a regression analysis approach applied to rich case data and quantitative results, we find that the reform labs have a significant impact on both participants and their reform projects in the short-term immediately after the event and in the medium term up to 5 years later. We also find evidence that the impact on individuals and projects drives broader social impact. We take a holistic approach to the knowledge brokerage of designing the reform labs and find that across contexts and project phases, but highly costly. In comparing the reform labs to best practices identified in the literature, we find evidence that knowledge exchange interventions of longer duration, with case-focused teamwork, and involving intensive researcher-participant interaction are more impactful. Additionally, we observe that diverse participants can drive impact and their needs must be considered.