This paper shows how nature (i.e., one's genetic endowments) and nurture (i.e., one's environment) interact in producing educational attainment. Genetic endowments are measured using a polygenic score for educational attainment, while we use birth order as an important environmental determinant of educational attainment. Since genetic endowments are randomly assigned within-families and orthogonal to one's birth order, our family fixed effects approach exploits exogenous variation in genetic endowments as well as environments. We find that those with higher genetic endowments benefit disproportionally more from being firstborn compared to those with lower genetic endowments.