Life skills, self-efficacy, life satisfaction and health literacy evolution from primary school to middle school: a 3-year longitudinal interventional study of the Explo'Santé cohort.

Introduction: Childhood and adolescence are decisive life stages during which social and health inequalities emerge and widen. Schools represent a privileged setting for health promotion, particularly through the development of psychosocial resources such as life skills (LS), self-efficacy (SE), life satisfaction (LSa), and health literacy (HL). The Explo'Santé program is a French school-based health promotion intervention that combines structured health education sessions with supportive environments. Methods: This longitudinal cohort study followed 744 pupils from 4th grade in primary school to the first year of middle school. LS, SE, LSa, and HL were assessed at six time points across three annual intervention cycles, each including ten weekly school-based health education sessions. Results: Linear mixed models showed short-term gains in LS, SE, and LSa during primary school, followed by a marked decline after the transition to middle school, whereas HL increased steadily throughout the 3 years. Girls consistently scored higher than boys but also showed sharper decreases once in 6th grade. Territorial disparities were observed, with some districts showing strong improvements while others consistently lagged. Discussion: These findings suggest that the Explo'Santé program supports the development of key psychosocial competencies, but that the transition to middle school represents a critical turning point which challenges their sustainability. By highlighting gendered vulnerabilities and contextual inequalities, this work contributes to understanding how schoolbased health promotion can foster more equitable developmental trajectories.