This paper presents the findings from two school-level randomized controlled effectiveness trials of a multitiered systems of support for behavior (MTSS-B) framework on student and staff reported school climate outcomes in 98 secondary schools. Schools randomized to the intervention condition received training and coaching to support Tier 1 implementation and the use of data for selection and implementation of Tier 2 and 3 evidence-based programs. Multigroup, multilevel regression analyses were conducted in Mplus to assess intervention effects on change over time in student and school staff perceptions of engagement, environment, and safety. Main effects models indicated limited impacts on student perceptions of school climate and negative effects for middle school staff perceptions. Moderation models indicated greater negative impacts for school staff perceptions in middle schools that had higher preexisting MTSS-B fidelity. These results highlight the challenges of demonstrating change in school climate outcomes. Additional theoretical and measurement work is needed on the assessment of changes in perceptions of school climate, particularly for school staff.