The purpose of this study was to examine associations between implementation fidelity of school-wide positive behavioral interventions and supports (SWPBIS) and student outcomes over time. The sample included 477 K-12 schools across 10 states implementing SWPBIS for varying numbers of years and at varying levels of fidelity (but with 78% of schools at or above established fidelity criteria). Results indicate that, in general, schools showed a decline in office discipline referrals (ODRs) and out-of-school suspensions (OSSs) over 3 years. SWPBIS fidelity of implementation was positively associated with initial levels of ODRs and OSSs, and the relations between fidelity and OSSs varied based on years of SWPBIS implementation. Levels of fidelity did not predict change in ODRs or OSSs. Despite no statistically significant associations between fidelity and student academic outcomes, schools that had implemented SWPBIS for 3 years or more had higher achievement in mathematics after controlling for prior achievement.