Previous research suggests that gains in positive mental health (often termed flourishing, wellbeing, or competence) is associated with stronger academic achievement. This study examines the relationship between positive mental health at school entry and academic achievement at Grade 3, drawing on a representative sample of Australian children with linkage to results of standardized academic testing. Propensity score analysis was used and small positive associations were found between positive mental health and most academic outcomes. Associations were modest in size but sustained over the 3-year period and were similar across a range of academic skills. Future intervention research should assess the potentially wider ranging impact of targeting positive mental health outcomes in the early years of schooling.