Well, some high ranking schools are said to admit a subset of minorities who can't do the work, which has a ripple effect on down. E.g. look at the "minorities as mascots" thesis, and I think Thomas Sowell has written on this.
MIT, for a bunch of reasons I've mentioned, plus intense self-selection in just deciding to apply in the first place, doesn't have this problem. Certainly didn't in the dozen years I was a member of the community, '79-'91, I never met a student who couldn't do the work.
Now, there are students who don't succeed because of financial issues (my problem, and one of at least one close friend), and personal issues (more than a few), but these are not things the admissions office can do as good a job in screening for.
MIT, for a bunch of reasons I've mentioned, plus intense self-selection in just deciding to apply in the first place, doesn't have this problem. Certainly didn't in the dozen years I was a member of the community, '79-'91, I never met a student who couldn't do the work.
Now, there are students who don't succeed because of financial issues (my problem, and one of at least one close friend), and personal issues (more than a few), but these are not things the admissions office can do as good a job in screening for.