There has been significant research on the association between hearing loss and academic achievement. However, many studies do not disaggregate by degree of hearing loss. Therefore, the risks to school performance posed by unilateral and mild bilateral hearing loss are not well understood, despite prevalence studies suggesting that 2.4 to 23% of individuals may be affected. This study systematically reviewed the existing published and unpublished literature to understand whether an association exists between academic achievement and unilateral and mild bilateral hearing loss for children of primary school-age. Following the identification of 16,269 articles from Web of Science, ProQuest and EBSCOHost, PRISMA guidelines were followed to screen the articles and analyse those that met the pre-specified inclusion criteria. The study identified 12 reports covering nine studies that met these inclusion criteria. Across all the studies, and for both unilateral and mild bilateral hearing loss, the majority of effect sizes were negative. This indicates that children with mild and unilateral hearing loss achieved lower mean scores in the assessments compared to their fully hearing peers for the majority of measures. Of the 57 effect sizes measured, 51 were negative, with similar ratios being observed for both unilateral and mild bilateral hearing loss measures. Of the 51 negative effect sizes, 27 were substantially important, defined as an effect size of at least 0.25. None of the positive effect sizes were substantially important. However, this analysis is based on a limited number of relatively small, heterogeneous studies. To fully understand the association between unilateral and mild bilateral hearing loss and academic achievement, more comprehensive studies that explore the association between school performance and these population groups would be a welcome addition to the current literature.