My friend Thomas Sowell writes:
... the mystical benefits of "diversity" are non-existent, however politically correct it is to proclaim such benefits.
Hard evidence shows that students of all races can succeed or fail in schools that are racially mixed or racially unmixed.
The latest variation on the theme of mixing and matching by race is that there needs to be a "critical mass" of black students in a given school or college, in order for them to perform up to standard.
Not only is there no hard evidence for this dogma, such hard evidence as there is points in the opposite direction.
http://jewishworldreview.com/cols/sowell121206.php3