Traditional professional development for teachers seldom results in program implementation with high fidelity or improved student outcomes. In this study, we evaluated the effects of performance feedback on the implementation of a class-wide, behavioral level system in four self-contained, secondary classrooms for students identified with emotional disturbance. Using a multiple-baseline across-participants design, we examined the effects of performance feedback on the treatment integrity of the level system, along with changes in student engagement and student disruptive behavior. Results indicated a clear functional relation between performance feedback and teachers' treatment integrity, with less of a relation observed between performance feedback and students' academic engagement or disruptive behaviors. Implications of these findings are discussed within the context of effective behavioral interventions for students with significant behavioral challenges.