Comment by verall

It is common and it is coupled with investment in improving schools in underprivileged neighborhoods.

A school in a poor area gets heavy investment and then can pull ("magnet") a certain percentage of their students from a much wider area. Involved parents apply for their children to go to these schools since they have the best art or theater or robotics or whatever programs.

This acknowledges that an important part of a successful school is parental involvement and a general culture of students that are interested in learning.

In practice, at least in my childhood, the schools largely self-segregated by the classes they took, i.e. AP or not, more or less challenging tracks ("honors" classes).

I still think it was a net positive. At least students in the underprivileged areas got access to these advanced programs, even if there were still social barriers. And as a kid from the suburbs, I got to meet kids outside of my suburban cohort - I think this was really valuable to me as a bit of a misfit.