> Social cohesion is probably stronger influenced by wealth disparity than diversity.

That's not what I've seen, anecdotally. In school, university, and work places, the friend groups I've observed and been a part of have primarily aligned around racial groups.

American schools, unis and workplaces probably already select for equal socio economic status to a degree.

Just some food for thought: How is the ratio of blue collar / white collar kids in your peer group? How close are you / were you in percentile distance?

No one caress for race in my environment, but even as a student somehow everybody I hang out with had the same amount of money.