Despite its polychromatic diversity, New York City has one of most deeply segregated school systems in the nation. When asked about this last week, Mayor Bill de Blasio dodged by saying that the schools are a reflection of historical housing patterns, and, “We cannot change the basic reality of housing in New York City.”

Segregation in the city’s schools cannot be dismissed as an unsolvable problem. And though housing plays a role, decades-old educational policies have reinforced inequality and placed many low-income black and brown children on the road to second-class citizenship.

The Times’s Elizabeth A. Harris and Ford Fessenden made that clear last week in “The Broken Promises of Choice in New York City Schools,” an investigation of how a school choice initiative actually traps many low-income children in an inferior system-within-a-system.

Created during the mayoralty of Michael Bloomberg, New York’s choice system frees eighth graders who once would have attended their neighborhood high schools to apply anywhere in the city. But many of the most desirable high schools seem to have washed their hands of all but the best-prepared students by basing admission on auditions, or scores on a one-day, high-stakes test, or top performance on statewide exams, or portfolios of middle school work. Others apply vague entrance criteria that leave a room for arbitrariness.