The racial segregation of schools is commonly cited as the foundational injustice of the U.S. education system and an ongoing impediment to educational equality. For liberal experts and reformers, school segregation is defined as a pattern of racially separate schools serving either White students or students of color. This paper argues that this prevailing understanding of the school segregation issue is intellectually inadequate and politically limiting. Drawing on a case study of Chicago’s movement for racial educational justice in the 1960s, I show that this simple framing of the issue initially gained prominence as an alternative to the more radical and contextualized critique of urban school segregation articulated by local Black grassroots activists. In contrast with official liberal discourse and reform proposals, Black urban activists in the early 1960s challenged school segregation as a set of educational policies and practices that render schools both separate and unequal, locking Black students out of more privileged White schools and contributing to the uneven development of schools across the racial divide. By recovering this suppressed grassroots critique of urban school segregation, this paper calls for a broader theorization of contemporary school segregation as dynamic and relational rather than a static statistical pattern that simply compounds the existing concentration of disadvantage within segregated neighborhoods.