Reducing Addiction through Prevention Infrastructure Development (RAPID) - Preventing opioid and other drug use problems before they begin or escalate provides substantial benefits to individuals, communities, and society. Effective upstream prevention and early intervention services can interrupt the progression of substance use problems, reducing the need for costly downstream treatment of substance use disorders (SUD). This is especially important for marginalized youth, who face elevated risk factors for SUDs and experience disparities in accessing necessary services. Schools offer a crucial setting for implementing evidence-based prevention and early intervention programs to mitigate these risks and promote positive development; however, schools lack the infrastructure required for sustained delivery and long-term impact of school-based services for youth at risk of SUD. This R61/R33 project, Reducing Addiction through Prevention Infrastructure Development (RAPID), addresses this critical need by building upon the research team’s prior work, Rapid Adaptation to Prevent Drug Use, to establish sustainable infrastructure for multi-tiered SUD prevention in high schools. RAPID employs a phased, mixed-methods approach, guided by implementation science frameworks and community-based participatory research principles. The R61 Phase will focus on adapting and refining a multi-phase implementation infrastructure-building blueprint, originally developed for Tier 1 (universal) prevention for use with Tier 2 (selective) and Tier 3 (indicated) SUD prevention evidence-based programs. The RAPID blueprint includes core strategy functions centered on (a) Partnerships, (b) Readiness, and (c) Resource Access. We will utilize the IDEA (Iterative Decision-Making for Evaluating Adaptations) framework, incorporating input from three community advisory boards comprising (a) program and practice experts; (b) school financing experts; and (3) individuals with SUD lived experience. RAPID is designed to leverage existing school strengths and ensure contextual relevance. The research team will review implementation financing strategies for school-based prevention and incorporate feasible strategy options and fiscal mapping to guide strategy selection and expand the resource access core strategy of RAPID. User-testing will be completed to ensure RAPID usability in advance of the R33 Phase. The R33 Phase comprises a rigorous evaluation of the effectiveness and cost-effectiveness of the RAPID implementation strategy compared to standard technical assistance. We will employ a stepped wedge cluster randomized design across 40 demographically and geographically diverse high schools in Michigan to assess the impact on program reach (primary outcome) and student outcomes (secondary; e.g., drug use). Economic analyses will utilize activity-based costing and trial-based modeling to determine the cost-effectiveness of RAPID. By integrating rigorous research methods with a deep commitment to community partnership, equity and stakeholder engagement, this project aims to serve as a replicable model for schools and communities nationwide, building the infrastructure needed to prevent opioid and other SUDs.