This article examines—for two developing countries, Vietnam and Peru—whether disadvantaged children learn less than advantaged children when both types of children are enrolled in the same school. This is done by estimating education production functions that contain two school fixed effects for each school, one for advantaged children and one for disadvantaged children. The article examines six different definitions of advantage based on household wealth, cognitive skills at age 5, gender, ethnicity (Peru only), maternal education, and nutritional status. The results show no sign that schools are less effective for disadvantaged groups in Vietnam; indeed, if anything one traditionally advantaged group, males, seems to do worse in school than the corresponding disadvantaged group, females. In contrast, in Peru ethnic minority students and students who enter primary school with low cognitive skills appear to learn less in school than ethnic majority students and students with relatively high cognitive skills, respectively, who are enrolled in the same school.