This study reports the long-term effects of a professional learning program for classroom teachers on fundamental motor skill (FMS) proficiency of primary school students from ethnically diverse backgrounds. Design: A cluster non-randomized trial using a nested cross-sectional design. Methods: The study was conducted in 8 primary schools located in disadvantaged and culturally diverse areas in Sydney, Australia. The intervention used an action learning framework, with each school developing and implementing an action plan for enhancing the teaching of FMS in their school. School teams comprised 4-5 teachers and were supported by a member of the research team. The primary outcome was total proficiency score for 7 FMS (run, jump, catch, throw, kick, leap, side gallop). Outcome data were analyzed using mixed effects models. Results: Eight-hundred and sixty-two students (82% response rate) were assessed at baseline in 2006 and 830 (82%) at follow-up in 2010. Compared with students in the control schools, there was a significantly greater increase in total motor skill proficiency among children in the intervention schools at follow-up (adjusted difference = 5.2 components, 95%CI [1.65, 8.75]; p. = 0.01) and in four of the seven motor skills. Conclusions: Training classroom teachers to develop and implement units of work based around individual FMS is a promising strategy for increasing FMS among ethnically diverse children over an extended period of time.