A Suburb Believed in Liberal Ideals. Then Came a New Busing Plan.

This suburb, with its high-performing schools, seems a haven of diversity and progressiveness. Signs that trumpet “Stigma-free Town” and “Hate Has No Home Here” hang from lampposts and, after a series of fatal police shootings across the country, “Black Lives Matter” placards popped up on lawns.

But now a strategy to tackle racial inequity in the school district is challenging the town’s self-image, casting a harsh light on segregation and the stark achievement gaps between black and white students — and raising pointed questions about race and class.

In the...