Developing and piloting My Life – I Decide combining co-design and realist methods: A health promoting school intervention for 10th grade students in Denmark

Objective Adolescents face multiple mental and behavioural health challenges, which impacts their health and educational attainment. The Health Promoting School (HPS) framework has been found to improve student mental health and well-being by integrating health into all aspects of school life including curriculum, environment, policies, and community partnerships. However, implementation of HPS approaches is challenged by competing academic demands, and insufficient commitment from practice and schools. This study describes the development and piloting of a HPS intervention, ‘ My Life – I Decide’ , aimed at fostering physical and positive mental health and school well-being among 10th-grade students (aged 15–17) in Denmark. The process was guided by co-design and realist methods and followed three steps: (1) Establishing the co-design and partnership foundation, (2) Co-designing and theorizing, and (3) Piloting and refining. Methods Empirical data included an evaluation by the municipality (practice) (n =1), research-practice meetings (n =4), student focus groups (n =4), observations (n =7), interviews with health consultants (n =7), teachers (n =4), school managers (n =2), and school-municipal workshops (n =2). Context-mechanisms-outcomes configurations were developed to inform intervention adaptations and program theory development. Results In Step 1, the research-practice partnership identified a need for an asset-based approach and systematic application of HPS components. In Step 2, a health education program was adapted via co-design and theorizing, which revealed that experiential learning and education outside the classroom should be promoted. A school-community component was developed to foster system-level impacts. In Step 3, teacher-health consultant collaboration and institutional support were mechanisms for implementation. Conclusion Future research should explore mechanisms for integrating HPS concepts into school and municipality policies.