While implementation research has studied the behaviors of street-level bureaucrats (SLBs) exten-sively, we have very little knowledge about the role of managers in affecting SLB behaviors during implementation of policy reforms. This report examines the role of managers in the implementation of a major – but contested – public school reform in Denmark. Testing change management theory, we find substantial effects of managerial communication about the change on the implementation of the reform in teaching practices – this concerns both communication of visions and plans for imple-mentation and conversations with employees individually about their future role. However, several other change management aspects have no effect or very slight effects on implementation. We also find substantial implementation effects of managers’ professional leadership when they are involved in teaching, i.e. when they observe classroom teaching, provide feedback and discuss methods. The study finds even stronger implementation effects of distributed leadership/professional learning communities of teachers. Finally, manager qualifications matter – not formal but informal qualifica-tions, as perceived by teachers. The management practices that are close to teachers seem to have the strongest impact on their implementation practices. Whereas the study finds strong and robust impacts of some management practices on implementation of the reform, it does not find any certain effects on school performance in terms of pupil learning and well-being. It might be too early to identify such impacts. The study uses school fixed-effect analyses based on annual panel surveys of school managers and teachers in a sample of schools, combined with administrative registry data from 2014 to 2016.