Supporting fidelity of implementation: Evidence from pathways-to-success replications.

= 92 schools with video-based fidelity data). We review the implementation fidelity literature, distinguish fidelity from implementation support and institutional climate, operationalize our state-of-the-art fidelity assessment and the supports we provided, describe results, and implications for scaling. Results reveal first that, on average, first-time implementing teachers implemented with above-threshold fidelity. Second, across years, teachers engaged with training, preparation, and delivery aids despite planned variability in teacher-trainers and teacher-training method (in-person, virtual) and natural variation in school climate, urbanicity, classroom size, and student features (English learner, free or reduced-priced lunch, standardized test proficiency, racial-ethnic composition). Third, implementation support matters. Continuous fidelity evaluation makes dynamic investment in implementation support possible; implying that scaling and sustainability require ongoing rather than proof-of-concept initial fidelity assessment. At the same time, new tools are required to contain costs. We are exploring use of artificial intelligence-based fidelity coding to address this issue. (PsycInfo Database Record (c) 2026 APA, all rights reserved).