Aim: To determine if the musculoskeletal benefits of a twice-weekly, school-based, jumping regime in healthy adolescent boys and girls were maintained three years later. Methods: Subjects of the original POWER PE trial (n = 99) were contacted and asked to participate in 36-month follow-up testing. All original measures were completed including: sitting height, standing height, weight, calcaneal broadband ultrasound attenuation (BUA), whole body, hip and spine bone mineral content (BMC), lean tissue mass, and fat mass. Physical activity was recorded with the bone-specific physical activity questionnaire (BPAQ) and calcium intake was estimated with a calcium-focussed food questionnaire. Maturity was determined by Tanner staging and estimation of the age of peak height velocity (PHV). Muscle power was assessed using a vertical jump test. Results: Twenty-nine adolescents aged 17.3 ± 0.4 years agreed to participate. At 36 months, there were no differences in subject characteristics between control and intervention groups (p > 0.05). Three-year change in weight, lean mass, and fat mass were similar between groups (p > 0.05), however, height increased more for the intervention group (+5.1%) compared with controls (+2.6%) (p = 0.05). There were no significant group differences in three-year change in BUA or BMC at any site (p > 0.05). Conclusion: Findings suggest that adolescents will maintain osteogenic benefits from an in-school jumping intervention at least into young adulthood.