This reminds me of an interesting story from Not In My Neighborhood, a history of residential and institutional segregation in Baltimore. Baltimore in many ways had three-way segregation -- black, white, and Jewish -- with Realtors for all three communities refusing to show houses in the "wrong" neighborhood to anyone. However, the public school system only had two-way segregation -- black and white, with Jews attending white schools.

Johns Hopkins, then as now an elite institution located in Baltimore, encouraged local kids to apply, and was integrated long before the public schools were. Hopkins never had any kind of restriction on the number of black students, but they did have quotas on the number of Jews. That's because the black school system was bad enough (and blacks generally financially disadvantaged enough) that they knew they'd never have more than about 5 percent or so of their student body being black -- enough to show that they were liberal and enlightened, but not enough to change the character of the student body. But if they let in all the Jews who qualified, the school would be half Jewish, which would be unacceptable, as they'd get a reputation as a "Jewish" school.

This is also one of the reasons for the long-ago heyday of City College in New York: as a public college, they didn't discriminate, and so a lot of Jewish kids who would have otherwise qualified to go to the Ivy League ended up there.