This study tested implications of new genetic discoveries for understanding the association between parental investment and children's educational attainment. A novel design matched genetic data from 860 British mothers and their children with home-visit measures of parenting: the E-Risk Study. Three findings emerged. First, both mothers' and children's education-associated genetics, summarized in a genome-wide polygenic score, were associated with parenting--a gene-environment correlation. Second, accounting for genetic influences slightly reduced associations between parenting and children's attainment--indicating some genetic confounding. Third, mothers' genetics were associated with children's attainment over and above children's own genetics, via cognitively stimulating parenting--an environmentally mediated effect. Findings imply that, when interpreting parents' effects on children, environmentalists must consider genetic transmission, but geneticists must also consider environmental transmission.