Throughout the 19th and 20th Centuries, the United States greatly expanded the role of public education. This infrastructure was built up unequally, with schools actively segregated by race. The separation of students by race helped to reinforce the existing racial hierarchy. This also has major implications for the wealth disparities between racial and ethnic groups.
Its really sad to think how schools gave better opportunities to white students and worse ones to students of color. That made it nearly impossible for everyone to have the same opportunities.