As the most penetrating longitudinal investigation of the subject, this research has unearthed fascinating new insights into school leadership that add real substance to the sum of our knowledge. It incorporates data from educational systems in Australia, Denmark, Norway, Sweden, England and the USA. One key finding is that while all principals delegate a range of leadership tasks, successful ones distribute responsibility on a case-by-case basis founded on personal assessments of their staff as well as on organizational and policy contexts. The research also demonstrates that successful principals maintain close communication with their staff and the wider school environment, and that they are adaptive, maximizing the opportunities presented by new political contexts and expectations, yet without losing sight of their school’s core moral and ethical principles. The volume’s international thematic analysis has allowed comparative conclusions to be drawn on what the principals do to sustain and foster pedagogical and institutional success.