It seems to be a common-sense argument that, if teachers know how to teach reading, or math, or any other subject, and if schools emphasize the importance of these tasks and permit no distractions, children should be able to learn regardless of their family income or skin color. But this perspective is misleading and dangerous. It ignores how social class characteristics in a stratified society like ours influence learning in school. For nearly half a century, the association between social and economic disadvantage and the student achievement gap has been well known to economists, sociologists, and educators. Most, however, have avoided the obvious implication of this understanding, that raising the achievement of lower-class children requires that public policy address the social and economic conditions of these children’s lives, not just school reform.