Gender imbalance in time spent on children causes labor market gender inequalities. We investigate a novel source of this inequality: external demands for parental involvement. We pair a theoretical model with a large-scale field experiment with a near-universe of US schools. Schools receive an email from a two-parent household and are asked to contact one parent. Mothers are 1.4 times more likely than fathers to be contacted. We decompose this inequality into discrimination stemming from differential beliefs about parents’ responsiveness versus other factors, including gender norms. Our findings underscore how agents outside the household contribute to gender inequalities.