School health promotion, based on a wide range of research and practice, has evolved over the course of the last 50 years, alongside health promotion in other settings. During the 1990s, WHO, working jointly with the European Commission and the Council of Europe, developed the health promoting schools initiative. It is a multifactorial approach that covers teaching health knowledge and skills in the classroom, changing the social and physical environment of the school, and creating links with the wider community. This synthesis seeks to determine the effectiveness of health promotion in schools and, more specifically, the effectiveness of the “health promoting schools” approach. The synthesis builds on the last comprehensive review in this field, published in 1997.