Consistent with the Williams v. California suit, our focus in this article is on educational equity, particularly the interface between equity and school organization. We concentrate on two structural issues, school size and school overcrowding, and one specific school structure, schools-within-schools. We organize the article as an interpretive summary of existing studies of these topics, concentrating on how these structural issues relate to social stratification in student outcomes, particularly academic achievement. Our evidence is drawn from both national studies and, when available and appropriate, from research that discusses the effects of school structure in California. We use this evidence to define which size high schools are best for all students (600-900 students), which responses to school overcrowding are appropriate (building more schools rather than adding portable classrooms or multitrack year-round schooling), and how creating smaller learning communities in high schools can work well for everyone by reducing the potential for internal stratification. California policies, however, have not promoted these responses. In many cases they have actually exacerbated inequality in educational outcomes and assisted the transformation of the social differences students bring to school into academic differences. We advocate reforms that are associated with high achievement and achievement that is equitably distributed by race, ethnicity, class, or family origin. Reforms that raise achievement of children at the lower end of the distribution without damaging those at the top are ones toward which we believe our nation should strive. By offering empirical evidence of practices that lead toward this important goal, we hope to inform the important debates surrounding the Williams case.