Quantitative genetic model fits White full siblings, White half-siblings, Black full siblings, and Black half-siblings equally. Achievement tests load on Genetic factor across all groups. Mathematics loads primarily on Shared Environment factor. Same genetic and environmental factors produce individual variation and racial group mean differences. Genes explain 66-74% of observed group differences in reading recognition and comprehension. Genes explain 36% of observed group differences in mathematics. Shared environment explains 34-26% of verbal achievement group differences. Shared environment explains 64% of mathematics group differences. Model imposes equal factor loadings across racial groups. No unique cultural or economic factors needed to explain racial gaps.