Objective: To identify the effects of a structured and multifaceted physical activity and recess intervention on student and adult behaviour in school. Design: Mixed-methods and community-based participatory approach. Setting: Large, urban, low-income school district in the USA. Methods: Data were collected at three time points over a 1-year period. Sources included recess observations at four elementary schools, in-class behavioural observations of fifth-grade students (n = 21) and focus groups with fourth- and fifth-grade students (n = 75). Results: Results suggested an increased amount of positive interactions between adults and students and a decreased amount of conflict in the playground post intervention. Results also suggested that a peer-leadership training programme had beneficial effects on students' classroom behaviour. Conclusion: Results from this study provide evidence that school recess can be used to teach social-emotional competencies that can impact student behaviour during recess and in the classroom.