Anxiety and depression are linked to lower academic performance. It is proposed that academic performance is reduced in young people with high levels of anxiety or depression as a function of increased test-specific worry that impinges on working memory central executive processes. Participants were typically developing children (12 to 13-years-old) from two UK schools. The study investigated the relationship between negative affect, worry, working memory, and academic performance using self-report questionnaires, school administered academic test data, and a battery of computerized working memory tasks. Higher levels of anxiety and depression were associated with lower academic performance. There was support for a mediation hypothesis, where worry and central executive processes mediated the link between negative affect and academic performance. Further studies should test these hypotheses in larger longitudinal samples. Implications for school psychology practice and interventions in schools are discussed. (Contains 2 tables and 3 figures.)