Abstract Introduction Introduced in 2014, Danish public schools are obliged to ensure that all pupils are physically active at least 45 minutes on average per day. Research shows that many schools have incorporated more physical activities, but it is challenging to include all children and ensuring sufficient quality of activities. The purpose of this presentation is to outline the preparation of an intervention with the aim of supporting schools and teachers implementing a physical active school day for everyone. MethodsRandomised controlled trials are recognised as the most valid design to obtain knowledge on ways to promote new approaches in different settings. However, this design can be criticised for not taking enough consideration of the complexity of the setting. Furthermore, many scientific school interventions are too detached from practice, which makes the value for society small. The design of the current research intervention is based on theoretical concepts of implementation, innovation and psychosocial well-being and will adopt a compatible, adaptable and scalable approach to school based physical activity promotion. ResultsResearch results will be targeted practical actions and applicable to in-class activity, activity breaks and PE. It will include outcomes on students’ physical activity, motivation, well-being and learning ability as well as outcomes relevant to school management and development of teaching practices ConclusionIt is crucial to consider the complex reality of school settings when conducting real-life interventions, and innovative study designs must be developed to maximize the return to society.