Purpose: The purpose of this paper is to examine four case studies from the International Successful School Principalship Project to explore and highlight how the role of the principal is critically important to sustaining school success. Implications for improving the preparation of aspiring and practicing school leaders are discussed. Design/methodology/approach: Data were collected using multiple sources, including documents and interviews with a variety of people including the principal, other school leaders, teachers, school council/board members, parents and students. Each case study was analyzed to understand how the principal and other leadership contributed to school success. Findings: There were several core dimensions of the principals' leadership that led to sustained school success. Principals clearly articulated views on education and helped their schools set appropriate directions. They were all concerned with the professional development of teachers to build capacity and teacher leadership. All principals were instructional leaders who influenced teaching and learning and were committed to making a difference. They exhibited other qualities such as resilience and their motivation to sustain their efforts over time. Another important dimension was building community. These principals reached out to their communities. They clearly understood that they could not succeed in isolation. Originality/value: The notion of sustainability in education remains ambiguous and this paper provides some empirical evidence of how successful school principals maintain school success over an extended period. Importantly, it considers how aspirant and practicing principals can be developed and supported in their efforts to lead and sustain successful schools.