There is general agreement about the benefits of school-based social and emotional learning (SEL) interventions in relation to children and young people’s social-emotional competence, mental health, and academic achievement. However, we know little about the theorized mechanisms through which SEL leads to improved academic outcomes. The current study is the first to present an integrative model using a 3-wave longitudinal sample of 1626 9–12-year-old students attending 45 elementary schools in England, drawn from a major randomized trial of a universal SEL intervention (the Promoting Alternative Thinking Strategies curriculum; PATHS). […] Collectively, the findings indicate some possible revisions to our current understanding regarding the role of social-emotional competence in promoting academic attainment, as its contribution appears to lay primarily in buffering the adverse effects of mental health difficulties.