There has been a long-lasting debate of whether the effects of family background are larger than those of school resources, and whether these effects are a function of national income level. In this study, we bring a new perspective to the debate by using the concepts of relative risk and population attributable risk in estimating family and school effects. The study uses data from the Programme of International Student Assessment (PISA), a large international comparative study of the skills of 15-year-old students in 43 countries. The study finds that: (1) there is a curvilinear association between family effects, measured by both relative and attributable risk, and national income level; (2) there is no association between school effects and national income level; (3) the risk associated with low levels of family background is larger than that of low levels of school resources, regardless of national income level. (Contains 4 graphs and 3 tables.)