To what extent do summer learning losses depend on ethnicity and socioeconomic status? Prior research indicates that poor students undergo larger summer reading losses than their middle-class counterparts, and all students undergo similar losses in math. To explain this finding, scholars have relied on surveys of summer activities, which show that poor children have fewer opportunities to practice reading than middle-class children. As a result, socioeconomic gaps in reading are heightened during summer vacation, suggesting that differences in family background—not differences in school quality—create achievement inequalities. Using data from a heterogeneous sample that includes all four major ethnic groups, this study reveals one predictable finding and one surprising finding. First, as suggested by prior research, summer reading losses are sensitive to income status. Low- income Asians and Latinos, and to a lesser extent low-income Blacks, lose ground in reading. Middle-income minorities also undergo reading losses, but these losses are smaller than those for low-income students. Second, low-income Blacks and both low- and middle-income Asians enjoy summer math gains, and the gains for middle-income Asians are especially large. This finding challenges the widely accepted research finding that all children’s math skills remain flat or decline during summer vacation. Suggested explanations for both sets of findings focus on home and community circumstances, which influence achievement during summer vacation. Researchers, policymakers, and educators should look outside of schools to understand why achievement gaps form and how to remedy them. This paper concludes with some recommendations for policy and future research.