BACKGROUND: School-based physical activity interventions such as The Daily Mile (TDM) are widely promoted in children's physical activity guidance. However, targeting such interventions to areas of greatest need is challenging since determinants vary across geographical areas. Our study aimed to identify local authorities in England with the greatest need to increase children's physical activity and assess whether TDM reaches school populations in areas with the highest need. METHODS: This was a cross-sectional study using routinely collected data from Public Health England. Datasets on health, census and the built environment were linked. We conducted a hierarchical cluster analysis to group local authorities by 'need' and estimated the association between 'need' and registration to TDM. RESULTS: We identified three clusters of high, medium and low need for physical activity interventions in 123 local authorities. Schools in high-need areas were more likely to be registered with TDM (incidence rate ratio 1.25, 95% confidence interval: 1.12-1.39) compared with low-need areas. CONCLUSIONS: Determinants of children's physical activity cluster geographically across local authorities in England. TDM appears to be an equitable intervention reaching schools in local authorities with the highest needs. Health policy should account for clustering of health determinants to match interventions with populations most in need.