Methods
We used cross-sectional data from the 2006- and 2010-survey of the Health Behaviour in School-aged Children study. The headmasters answered questions about the school’s participation in health promoting activities and about school size, proportion of ethnic minorities, school facilities available for health promoting activities, competing problems and resources at the school and in the neighborhood. Students provided information about their health-related behavior and exposure to bullying which was aggregated to the school level. A total of 74 schools were available for analyses in 2006 and 69 in 2010. We used chi-square test, t-test, and binary logistic regression to analyze time trends and differences between schools engaging in many versus few health promoting activities.