<p>Health literacy is critical for health promotion and equity, yet limited evidence exists on how it can be supported among socioeconomically disadvantaged adolescents. Given the importance of schools in promoting adolescent health, this study reviewed school-based health literacy interventions targeting socioeconomically disadvantaged adolescents aged 13–24, with a secondary focus on participatory implementation strategies. A comprehensive search across six databases identified 7152 records published between 2010 and 2024, of which 26 met the inclusion criteria. Eligible studies included randomized controlled trials, non-randomized studies, qualitative studies, and mixed-methods designs. Study quality was assessed using the Mixed Methods Appraisal Tool. Most interventions focused on physical activity, diet, or mental health, but none explicitly measured health literacy. However, health literacy-relevant components were common, especially functional health literacy, while critical health literacy was nearly absent. While educational, hands-on learning and participatory approaches were often employed, student involvement was limited, and few interventions addressed the broader social and structural context influencing adolescent health literacy. The findings underscore the need for youth-centered approaches, improved conceptual clarity, and greater attention to the socioeconomic and cultural context. Strengthening school-based strategies in this way is crucial for supporting health equity during a key developmental period.</p>