The national Finnish Schools on the Move programme support schools with their individual plans to promote school-based physical activity (PA). We examined the changes in adolescents' recess and overall PA in four lower secondary schools and described the school actions to promote students' PA and the local contact persons' perceptions of the effects. Recess and overall PA were assessed four times by anonymous questionnaires from students in grades 7-9 (n = 789) in 2010-12, and local contact persons (n = 7) provided information on school actions with diaries, interviews and surveys. Student data were analysed with descriptive statistics and chi-square tests, and school actions data were analysed with quantitative content analysis. The proportion of students who participated in physical activities at recess at least sometimes increased from 30% to 49% in physically active play and from 33% to 42% in ball games, mostly due to improvements in males' participation. Females' participation in recess activities increased in two schools with gender-specific physical activities or facilities. Overall PA levels declined slightly. Organized recess activities, student recess activators and equipment provision and sports facilities development were considered to have affected students' PA positively. Solutions for getting females more physically active in the school setting are needed.