Purpose: The purpose of this paper is to examine the effects of leadership on student achievement and sustained school success, especially in challenging, high-poverty schools. Design/methodology/approach: The paper combines a review of the leadership literature with findings drawn from longitudinal studies of the International Successful School Principalship Project (ISSPP). Findings: Direction setting, developing people and redesigning the organization were practices common to successful principals in all contexts, including those in challenging, high-poverty schools. How these practices manifested varied in relation to national context and tradition. Distributed teacher leadership and professional self-renewal emerged as processes central to sustaining success, and, in at least one US case, a change in organizational governance was necessary to allow these processes to continue over time. Originality/value: The paper adds to the literature on leadership effects on student achievement and sustaining school success, especially in challenging high-poverty schools.