We study differences in parental time investments in preschool girls and boys in Canada, the United Kingdom, and the United States. We find that investments in teaching activities like reading favor girls, starting at very young ages. We document that these boy/girl differences may be quantitatively important in explaining corresponding school-age test score gaps. We explore a parental preference explanation of these results. We find little support for a parental preference for girls (or boys) at young ages. As a result, the investment gaps may be due to sex differences in production functions or in the costs of delivering human capital investments.