Although the effort to restructure the American high school is in high gear, little attention has been directed to how changes in high schools' organizational structures might affect the dynamic of equity in student learning--the ways that schooling outcomes reflect students' social background. This paper aims to identify organizational properties of schools that are simultaneously associated with both effectiveness and equity, with a focus on equity. The investigation addresses the ways that achievement gains in mathematics and science correspond to the social distribution of family socioeconomic status. Using data from the first three waves of the National Education Longitudinal Study (1988), researchers compared the equity of achievement between schools that follow restructured reform practices to those following more traditional practices. In addition to finding improved achievement and equity in restructuring schools, the study identified specific characteristics of these schools' academic and social organization that help explain their improved student performance. These include smaller school size; a restricted, unified academic curriculum; and a strong commitment to viewing learning resources as a public, rather than a private good. Included are several tables and 36 references. (Author/MLH)