Middle school special education teachers often express concern about challenging student behavior. Class-Wide Function-Related Intervention Teams (CW-FIT), a behavior management program based on school-wide positive behavior support, have been effective in elementary general education classrooms. The present study, the first to apply it in a middle school special education setting, used an ABAC design to examine effects on student on-task behavior and teacher praise rates in a self-contained special education classroom for students with severe disabilities and their typically developing peer tutors. Results suggested that CW-FIT Tier 1 is associated with improvements in student on-task behavior and teacher praise rates, especially when peer tutors are included in the intervention and when the timer is silent. Both teachers and students reported the intervention to be socially valid. Study limitations and areas for future research are addressed.