Increasing physical activity is vital for children's physical and mental health. It is important to address inactivity early and engage children in positive behaviours which can be sustained throughout life. Teachers are well placed to understand and influence in-school factors impacting children's physical activity. As wearable technologies continue to improve and become more accessible, they offer the opportunity to engage schools in the data collection process, as well as providing them with the capacity to monitor strategies designed to improve physical activity. This study is a within-subject, pre-post, co-developed intervention design.

Previous interventions have not successfully increased physical activity levels in primary schools. This is arguably due to a lack of comprehensive data collection methods and the lack of co-involvement of teachers and children in intervention design. In previous research, accelerometers have been used by researchers to quantify children's physical activity levels. However, these have been research-grade devices which require a more complex analysis to extract results; because of this, these types of measurement tools have not been utilised by schools. This study will aim to utilise user-friendly technologies which can engage schools in the data collection process and be employed by schools to implement and measure strategies designed to increase physical activity by providing immediate feedback.

This project aims to investigate whether data from wearable technologies can be used to inform primary school-based practices and improve children's physical activity within school hours using co-developed interventions. This project is a participatory mixed-methods design in two phases. 7-9 schools will be recruited. The first phase in each school involves baseline measures of pupils' physical activity for 2-weeks, using accelerometers which have been specifically designed for school use. Pupils will be blinded to the physical activity data during this period. During this 2-week baseline teachers will be instructed to carry out lessons as normal, not changing their behaviour, or encouraging the pupils' physical activity. Data visualisations will be created from the 2-weeks of physical activity data collected within each school. Teachers will then be interviewed online, using Microsoft Teams, and encouraged to reflect on the physical activity data and co-develop 3-5 action points or strategies to increase children's physical activity. Teachers will then be asked to implement these action points over the subsequent 2-weeks, where again children's physical activity will be measured with the accelerometers. This time children will not be blinded to the data and can receive physical activity feedback if this is a strategy selected by their teacher. These changes will be at each schoolteacher's discretion and managed in a way they deem most appropriate. Following these 2-week changes teachers will be interviewed again about their experiences of using the technology and implementing strategies to encourage physical activity. They will then be shown similar data visualisations as before, comparing changes in pupils' physical activity between each 2-week period.

Inclusion Criteria:

• Any pupil from the each respective UK-based school and class. Pupils in years 5 to 6 (aged 9-11 years old).

Exclusion Criteria:

• No exclusion criteria.

Teachers input the gender pupils identify with into the physical activity data collection software.