Montgomery County, Maryland, operates one of the most acclaimed large public school systems in the United States. Although an increasing share of the population of this suburban school district just outside Washington, District of Columbia, is low income, and the majority of its students belongs to racial minority groups, the county graduates 9 in 10 of its students. Montgomery County's reputation as both an affluent area with good schools and a district that serves low-income students relatively well is firmly established. Much less known is the fact that it operates the nation's oldest and largest inclusionary zoning program--a policy that requires real estate developers to set aside a portion of the homes they build to be rented or sold at below-market prices. Building on the strength of the random assignment of children to schools, the author examines the longitudinal school performance from 2001 to 2007 of approximately 850 students in public housing who attended elementary schools and lived in neighborhoods that fell along a spectrum of very-low-poverty to moderate-poverty rates. In brief, the author finds that over a period of five to seven years, children in public housing who attended the school district's most-advantaged schools (as measured by either subsidized lunch status or the district's own criteria) far outperformed in math and reading those children in public housing who attended the district's least-advantaged elementary schools. In this report, the author describes the study, the findings, and their ramifications.