I think most people agree that there are extremes. There probably exists a small number of people who literally cannot (just like how 1 in a million could probably teach themselves calculus at age 10, also exists). However it's a big jump to conclude that even a small percentage of the people at your college cannot in the literal sense - i.e. if their life depended on it, they had all the resources they could want, they had no other distractions.