Abstract
More insight into the health effects of scaled-up school-based interventions in real-world settings is vital to sustainably integrate health in all schools. This study investigated the effectiveness of the scaled-up Healthy Primary School of the Future (HPSF) initiative in real-world school contexts on children's health (behaviours). From 2019 to 2022, eleven Dutch primary schools implemented HPSF-related activities. In 315 children from study years four to six (aged 7-11 years) from these schools, anthropometric measurements were performed, and questionnaires assessing the children's dietary behaviours and physical activity were administered. COVID-19 greatly limited the implementation of HPSF-related activities. Therefore, the results were compared between schools categorised as medium implementers and schools categorised as low implementers. After correction for baseline, waist circumference in the medium implementer group was significantly higher at one-year follow-up (B = 1.089, p = 0.003) and two-year follow-up (B = 1.665, p < 0.001) compared with waist circumference in the low implementer group. No significant effects were observed for other outcomes. This study showed hardly any effects of the scaled-up HPSF initiative, mainly due to the limited implementation caused by COVID-19. More research investigating the real-world effectiveness of HPSF and comparable programmes is greatly encouraged to advance the field of school-based health promotion.