Introducing an educational innovation into any school context involves some challenge to existing practices. Transition Year is an innovative, optional, one-year programme taken by approximately half the 15-16-year age cohort in schools in the Republic of Ireland. Based on data from an extensive study of TY operating in six different schools, programme co-ordinators and school principals are identified as having key roles in the successful implementation of TY. However, exercising the collegiality both roles demand goes against established cultures of isolated individualism in Irish schools. Furthermore, maintaining TY’s coherence and integrity in the face of threats from more established programmes offers particular challenges. For this innovation to be successful, active curriculum leadership by school principals is seen as crucial. The paper interrogates the evidence through the lens of the 2008 OECD study on school leadership and poses questions about the relevance and value of the OECD perspective.