The utility of music training in schools has received much attention in the United States. The purported positive cognitive benefits of music training for schoolchildren is one facet which has historically been used to advocate for the existence of public school music programs. The purpose of this study was to conduct a random-effects meta-analysis to measure the overall mean effects of music training on cognitive measures in schoolchildren. Results showed small to medium overall effects (N = 5,612, k = 100, g = 0.28, p < 0.001, 95% confidence interval [CI] [0.21, 0.34]). When compared to active control groups, music training yielded more improvement on a range of cognitive measurements (g = 0.21, p < 0.0001). While some studies did result in large effect sizes, significant moderators related to methodological quality rendered the overall findings non-significant (g = 0.08, p = 0.19, 95% CI [-0.04, 0.20]). Additional moderator analysis showed no clear advantage in one area of cognitive function. Results did not differ by geographical locale or type of music intervention. Overall, results suggested music training may be a positive cognitive intervention for schoolchildren; however, advantages as to the utility of music training compared to other cognitive interventions were less empirically supported.