Educators across the United States have designed and implemented Comprehensive, Integrated, Three-tiered (Ci3T) models to meet K–12 students’ academic, behavioral, and social and emotional well-being needs. As part of implementation efforts, educators collect and use social validity and treatment integrity data to capture faculty and staff views of the plan’s goals, procedures, and outcomes and the degree to which the plan is implemented as designed (e.g., procedures for teaching, reinforcing, and monitoring). In this study, we re-examined the relation between social validity and treatment integrity utilizing hierarchical linear modeling with extant data from a research partnership across 27 schools in five midwestern districts. Findings suggested an educator’s fall and spring social validity score on the Primary Intervention Rating Scale (PIRS) predicted their treatment integrity scores on the Ci3T Treatment Integrity: Teacher Self-Report (CI3T TI: TSR) in the same timepoint. Schoolwide average fall PIRS scores also statistically significantly predicted spring Ci3T TI: TSR scores. Results suggested schoolwide context is important for sustained implementation of Tier 1 procedures during the first year. Findings demonstrate the complex nature of implementing a schoolwide plan, involving each individual’s behavior while also relying on others to facilitate implementation. We discuss limitations and future directions.