Effective school leadership is widely acknowledged as having a positive impact on student achievement. However, there appears to be no deliberate process to sustain New Zealand principals' effectiveness throughout their careers. This article discusses the views of current and former New Zealand secondary school principals about their complex role and the support they believe would help them make sense of the role and its inherent challenges. The findings suggest that while principals develop tacit knowledge from learning on the job, they have little opportunity to engage in the critical reflection needed for ongoing learning and development. Their suggestions for systematic and mandated support are provided.