Opportunity hoarding is a sociological concept first introduced by Charles Tilly. This article explores its utility for historians by examining efforts to exclude different groups of people in a major American metropolis during the 1960s and seventies. This was a period of significant social change, as the racial composition of big city schools shifted dramatically and suburban school districts grew substantially. An examination two such suburban districts finds sustained and effective measures undertaken to exclude African-Americans from moving into one of them. In the neighbouring district, resistance to low-income housing was initially successful but white residents were unable to prevent relatively affluent blacks from settling there. This eventually contributed to further white flight and the transition to a predominantly African-American district. Mechanisms of exclusion are discussed, along with the utility of opportunity hoarding as a concept for historians interested in studying similar issues in other settings.