When equal resources fail to produce equal opportunity: a critical narrative mini review of implementation equity in school-based physical activity for adolescents.

Schools are the most universal platform for promoting adolescent physical activity (PA), yet uniform mandates have not produced equal opportunities. This Mini Review is a critical narrative (integrative) review: its objective is conceptual integration across three literatures that have developed separately, participation disparities, implementation determinants, and PA policy analysis, rather than pooled effect estimation, and it is reported in line with SANRA. We searched PubMed and the Web of Science Core Collection for evidence published between January 2021 and June 2026, supplemented by seminal sources identified through citation tracking, to examine implementation equity: the fair distribution of organizational capacity, accountability, and support required to convert policy and resources into sustained, high-quality activity opportunities. Existing syntheses have separately quantified participation inequities, appraised policy-practice associations, and evaluated intervention scale-up; none has made the school's organizational capacity to convert resources into opportunity the equity-relevant unit of analysis, and evidence from low- and middle-income countries (LMICs) remains peripheral to this literature. Three conclusions emerge. First, participation inequalities remain substantial and intersectional, with socioeconomic disadvantage, gender, disability, race and ethnicity, migration background, and rurality combining to restrict access. Second, implementation capacity is often distributed inversely to need. Schools serving disadvantaged populations face lower organizational readiness, staffing and time constraints, competing academic priorities, and policies that frequently lack funding and accountability, a pattern documented in high-income systems and LMICs alike. Third, implementation support, including school champions and teams, cross-sector partnerships, co-design with marginalized groups, and structured adaptation during scale-up, can strengthen delivery in high-need settings. However, equity effects remain poorly evaluated because studies emphasize reach and effectiveness while rarely assessing representative adoption or long-term maintenance. We identify four unresolved controversies and argue that equity should be treated as a primary implementation outcome rather than a background covariate. Equity-explicit reporting, intersectional analysis, participatory governance, proportionate support, and cross-sector accountability are needed to ensure that equal policy commitments generate genuinely equitable opportunities for adolescent physical activity.