School leaders play an important role in ensuring and enhancing the quality of schools. Continuous professional development and training of school leadership has for this reason become increasingly important in many countries. This article presents trends in the development of school leadership. Examples from selected European countries and curricula are presented. Trends that are identified pertain to the domains of leadership practices; leadership and sustainability; and leadership needs. The article elaborates on two domains: (1) the use of self-assessment and feedback as part of the professional development of school leaders, (2) the impact of professional development, that is, the ways in which theory and knowledge is translated to practices. Moreover, approaches to research on, and evaluation of, the quality of school leadership development are described as well as the World School Leadership Study (WSLS) and its potential for international comparative research as it, seeks to inform practices and contribute to policy and academic discourses on the provision of professional development for school leadership.

As a result of our comparative review of professional development of school leaders, we propose for the design and implementation of professional development to use multiple learning approaches. We also propose for the evaluation of the quality of professional development to take a wide range of didactical aspects and different levels of impact into account, from the increase in competence to the change in performance and its consequences in the school. Furthermore, ideally speaking, the evaluation draws on various sources, besides participant perception also the views of others, like, for example, the staff in school.