There is increasing recognition that effective leadership and management are vital if schools are to be successful in providing good learning opportunities for students, and emerging evidence that high quality leadership makes a significant difference to school improvement and learning outcomes. However, in many countries, including South Africa, a teaching qualification and teaching experience are the only requirements for school principals. In the 21st century, there is a growing realisation that headship is a specialist occupation that requires specific preparation. In 2007, the former South African Department of Education introduced a new threshold qualification for aspiring school principals as part of its wider strategy to improve educational standards. The course, badged as an Advanced Certificate in Education: School Leadership (ACE), was piloted in six provinces from 2007-2009. This paper reports the main findings from the evaluation of the pilot ACE programme and links them to the South African and international literature on leadership development.