Yes, andie's right, the social psychological research on this is quite clear: segregation breeds prejudice and institutional discrimination, and integation is an effective strategy for undermining these forms of inequality. Granted, integration is not always effective (what social intervention is?), but we know it's more effective than segregation.
[WS:] I am not so sure. My son went to a public "integrated" school in Baltimore reflecting the ethnic composition of the city (about 65% Black). There was a lot of talk there about racism and integration, but at the end of the day the circles of friends, dating, etc. were pretty much segregated.
I think we tend to grossly overestimate the effect of schools. They have some effect, to be sure, but they pale in comparison to the effect of community, parenting etc, which remain as segregated as ever. With that in mind, the ethnic composition of schools is but a shadow cast by the ethic composition of society and communities. The attenuation of that shadow will have a rather negligible effect on the latter.
I my view, integrated housing will have a far greater effect than the well intended but largely ineffective efforts to integrate schools.
Wojtek