@CateCAParent The diversity of a public school district mirrors the diversity of the community.
Because the USA is still highly segregated, most non-magnet public schools are not diverse. However, on average, magnet schools are more diverse than selective private schools. For example, the diversity of Walter Payton School and Northside Prep in Chicago reflects the diversity of the Chicago community as a whole (URM making up 30%-40%). If we look at selective private high schools, the percent URM is under 14%, as a general rule.
The community in which my kid grew up is diverse, and so the high school is diverse, with 32% Black or Hispanic. It is also a pretty good high school.