Many factors affect children’s well-being in adulthood. In this brief, we identify the life stages and aspects of children’s development that provide the most leverage for improving their outcomes in adulthood using simulations from the Social Genome Model, version 2.1. We find that improving math scores by 0.5 standard deviations for children up to age 12 is associated with larger increases on age-30 earnings than other equivalent improvements in reading, health, and relationship quality. The impact of math scores on earnings increases as children age until age 12. Improving math scores raises earnings at age 30 for children of all races and ethnicities by roughly the same amount in percentage terms in each life stage, with Hispanic children consistently seeing the largest gains. Girls tend to see a higher earnings boost than boys. Improvements in health during childhood lead to larger adult earnings gains in percentage terms for Black and Hispanic children as compared with white children.