BackgroundInternationally, government policies mandating schools to provide students with opportunities to participate in physical activity are poorly implemented. The multi-component Physically Active Children in Education (PACE) intervention effectively assists schools to implement one such policy. We evaluated the value of investment by health service providers tasked with intervention delivery, and explored where adaptations might be targeted to reduce program costs for scale-up.MethodsA prospective trial-based economic evaluation of an implementation intervention in 61 primary schools in New South Wales (NSW), Australia. Schools were randomised to the PACE intervention or a wait-list control. PACE strategies included centralised technical assistance, ongoing consultation, principal's mandated change, identifying and preparing in-school champions, educational outreach visits, and provision of educational materials and equipment. Effectiveness was measured as the mean weekly minutes of physical activity implemented by classroom teachers, recorded in a daily log book at baseline and 12-month follow-up. Delivery costs (reported in $AUD, 2018) were evaluated from a public finance perspective. Cost data were used to calculate: total intervention cost, cost per strategy and incremental cost (overall across all schools and as an average per school). Incremental cost-effectiveness ratios (ICERs) were calculated as the incremental cost of delivering PACE divided by the estimated intervention effect.ResultsPACE cost the health service provider a total of $35,692 (95% uncertainty interval [UI] $32,411, $38,331) to deliver; an average cost per school of $1151 (95%UI $1046, $1236). Training in-school champions was the largest contributor: $19,437 total; $627 ($0 to $648) average per school. Educational outreach was the second largest contributor: $4992 total; $161 ($0 to $528) average per school. The ICER was $29 (95%UI $17, $64) for every additional minute of weekly physical activity implemented per school.ConclusionPACE is a potentially cost-effective intervention for increasing schools implementation of a policy mandate. The investment required by the health service provider makes use of existing funding and infrastructure; the additional cost to assist schools to implement the policy is likely not that much. PACE strategies may be adapted to substantially improve delivery costs.Trial registrationAustralia New Zealand Clinical Trials Registry ACTRN12617001265369; Prospectively registered 1st September 2017 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=373520