In this article, we report the results from a randomized evaluation of the Safe and Civil Schools (SCS) model for school-wide positive behavioral interventions and supports. Thirty-two elementary schools in a large urban school district were randomly assigned to an initial training cohort or a wait-list control group. Results suggested that SCS training positively affected school policies and student behavior. Surveys administered after the commencement of SCS training found large improvements in staff perceptions of school behavior policies and student behavior at schools receiving SCS training that were not observed at wait-list schools. Similarly, we observed reductions in student suspensions at schools implementing SCS that were not observed at control schools. The observed improvements persisted through the second year of trainings, and once the wait-list control schools commenced SCS training, they experienced similar improvements in school policies and student behavior.