This study examined the impact of a state policy requiring that any school with a habitual truancy rate of 8% of higher to be trained in Tier 1 school-wide Positive Behavioral Interventions and Supports (SW-PBIS). A regression discontinuity (RD) design was used to examine how the schools' mandate status related to SW-PBIS training as well as student suspensions, truancy, and achievement in 410 public middle and high schools, of which 261 were affected by the mandate. We further examined the growth trajectories (i.e., improvement) of implementation fidelity over time using growth mixture modeling (GMM). Contrary to the intent of the policy to improve student outcomes, the RD results suggested the mandate did not impact reading and math achievement, truancy rates, or SW-PBIS training in 2010-11 through 2013-14. Mandated schools did have higher suspension rates in 2010-11 through 2013-14 than the non-mandated schools, however, these differences in the suspension rates appear to have persisted from years prior to the mandate. Descriptive analyses suggested that mandated schools had statistically significantly higher rates of training, and the GMM analyses on the fidelity data indicated that mandated schools were significantly more likely to be in an improving growth trajectory over time. Taken together, results suggested that the policy showed some promise for improving SW-PBIS training and fidelity over time, but it had little to no impact on student outcomes.