As a second year undergrad at a UC, I've found that the majority of the people who would appear to not have the cognitive capacity to excel in college courses were simply lacking in fundamental learning that they should have learned in high school or even middle school. All of the students I met that had trouble with calculus had trouble because of their poor algebra skills. The same is true of English classes where students had poor grammar and generally no concept of how to write a structured thesis-driven argument. Even in my upper div algorithms course, the only people who are doing poorly are the ones who did not pay attention in earlier cs classes where we already learned half of this stuff!

Clearly some people are truly incapable of excelling at these things, but I don't think that's the majority and I feel that if we could teach people better in k-12 then they would most definitely excel at higher learning schools where k-12 knowledge is expected.

But then again I'm young, so what do I know?