This study examined the impact of a classroom-level component of The Inclusive Skill-building Learning Approach (ISLA), an instructional and restorative alternative to exclusionary discipline, on student behaviors and school discipline practices in middle schools. Intervention implementation, classroom observations, and all other data collection took place once schools resumed in-person instruction during the COVID-19 pandemic, thus the study design was modified to a quasi-experimental design that included a control sample. Findings showed that focusing on classroom-level prevention alone increased students' active engagement, decreased disruptive behaviors, and resulted in lower rates of exclusion from the learning environment for treatment schools. [This is the online first version of an article published in "Journal of Education."]