The idea of matching the level of preparation is a very important one, not just for URMs but for everyone, and at all levels of schools. In fact one of the negative aspects of an MIT, caltech, or harvard is that it can take a very bright student who is very interested in math or physics and turn them away from majoring in the subject. If many of your peers have spent thousands of hours in the subject before entering college (e.g. average number of hours for math olympiad contestants) but you haven’t, you won’t catch up for several years (if ever). I’m not really a Malcolm Gladwell fan, but his idea in David and Goliath, that you are much more likely to succeed in life if you graduate in the top percentage of your class, from a second or third tier school, rather than in the bottom half of your class, from a tippy top, matches what I’ve seen.