There are studies showing that racial difference between black students and the majorly white faculties in most (read: all) Ivy League institutions disadvantages black students from forming relationships with professors and being willing to do things like go to office hours and ask questions and whatnot. Emotional outlets and such matter to one's college experience as well, and a predominantly white student body can inhibit that and raise stress levels.
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Also, do badly is an exaggeration. The graduation rates are within ten points of difference. Overall, graduation rate gaps have been decreasing over time. Furthermore, in smaller colleges, blacks outperform whites (Smith, Macalester, Wellsley).
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There are also confounding variables. Lower-income students tend to underperform in Ivy Leagues (specifically, the negative effect is greater in Ivys than in other types of schools) as well.
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I had to upload these to Dropbox because ordinarily you probably wouldn't be able to access them. I'll take down the Dropbox links at some point, probably.
Your claims are misrepresentative and overblown. As usual,
again, your argument is reductionist and absolutist, and assumes one simple, unsubstantiated explanation for a phenomenon that other studies have illuminated much more rigorously. Most claims founded on prejudice are just intellectually lazy, and this thread is an example of that.