That some students at even the most elite colleges may struggle with quantitative courses really shouldn’t be surprising considering that they may have gotten in because they are or have done some combination of the following:
-Recruited athlete
-Started a campaign to vaccinate/feed/fund 3rd world villages
-Been editor of a top-ranked HS newspaper
-Wrote poetry that is nationally acclaimed
and etc., none of which show any potential to be able to do anything quantitative.
Someone I know mentioned that in his b-school class was a guy who graduated from Princeton. He could write really well, but had trouble with stuff like figuring out what (x-y)^2 was equal to.