This study investigates the differences in the degree of low academic achievement of third and fourth graders living with single-parent families from 11 industrialized countries. The United States ranks first among the countries compared in terms of the achievement gap for children in single- and two-parent families. After controlling for individual and family variables, the gap in the United States shrinks somewhat, but American single-parent children are still more disadvantaged than those in the other countries. Following a cross-national multilevel analysis, which includes family policy and demographic variables at the national level, the study finds single parenthood to be less detrimental where there are family policies equalizing resources between single-parent and other families, such as family or child allowances and parental leave. It also finds that single parenthood is most detrimental for academic achievement in those countries where the percentages of single-parent families are the highest. Findings suggest that policies aimed at increasing family income can offset the detrimental achievement consequences of single parenthood. (Contains 63 references.) (Author/SM)