Implementing educational innovations is far more complex than the straightforward execution of policy prescriptions. The diversity in implementation variants reflects an inherent tension between stabilizing and change-driven processes in school organizations. This article tries to capture this complexity by focusing on how individual and collective processes of sense-making, as well as the actual structural factors (e.g., subcultures, roles and positions) and processes (e.g., legitimation) in the school, mediate implementation practices. Drawing on data from semi-structured interviews, this article reports on an exploratory study into the perceptions and implementation of the new statistics curriculum by secondary school teachers in Flanders (Belgium). (Contains 3 tables.)