OBJECTIVE: A quasi-experimental cluster-controlled design was used to test the impact of comprehensive school physical activity program (CSPAP) professional development on changes in school physical activity (PA) offerings, moderate-to-vigorous physical activity (MVPA) and sedentary behaviors of 9-14 year-old children during school. METHODS: Two groups of Louisiana elementary and middle school physical education teachers (N = 129) attended a CSPAP summer workshop (95 in 2012 = intervention, 34 in 2013 = control) and were assessed on school PA offerings (teacher-reported; pre, mid, and post). During the 2012-2013 school year, intervention teachers received CSPAP support while implementing new school PA programs. MVPA and sedentary behaviors were assessed (accelerometry; baseline and post) on a sample of 231 intervention, 120 control students from 16 different schools. RESULTS: Multivariate analysis of covariance indicated that intervention teachers reported significantly more PA offerings during school (3.35 vs. 2.37) and that involve staff (1.43 vs. 0.90). Three-level, mixed model regressions (stratified by sex) indicated that students overall spent less time in MVPA and more time being sedentary during school, but the effects were significantly blunted among intervention students, especially boys. CONCLUSIONS: This study provides preliminary evidence for CSPAP professional development programs to influence school-level PA offerings and offset student-level declines in MVPA and increases in sedentary behavior.