This study examined the relationship between the level of implementation of the Multi-Tiered System of Supports (MTSS) approach to service delivery in schools and educators’ beliefs regarding MTSS, their perceptions of MTSS practices in their schools, and student growth. The study used data from the Florida Problem Solving/Response to Intervention Project. Thirty-four pilot schools in seven school districts across the state of Florida were provided intensive coaching, training, and technical assistance in implementing the MTSS service delivery model for three years. The current study focused on the final year of support. Data collected as part of the project’s program evaluation model were used to examine the relationships between study variables. Multiple regressions were conducted to determine the relationship between the level of implementation of MTSS and the study’s dependent variables. Findings indicated that both Infrastructure and Implementation predicted educator beliefs about Data-Based Decision Making (DBDM), while Implementation alone predicted educator beliefs about the Academic Ability and Performance of Students with Disabilities (SWD). Furthermore, the overall regression model predicted educator perceptions of practices applied to both Academic and Behavior Content; however, none of the individual predictors were significantly related to either dependent measure. No other study dependent variables were significantly predicted by the level of MTSS implementation. Implications for practice and research involve the need for larger scale studies of MTSS implementation and the importance of researchers and practitioners utilizing reliable and valid measures to monitor implementation efforts.