It's actually more the norm than folks think. Student athletes come from several sports not just football BUT even if we just take football there's an NCAA limit of 85 on scholarship players (often called a roster limit but that's kind of a misnomer) + ~20 or so walkons for a total of 105 players. The majority aren't dumb. Not saying a lot aren't but not the majority. I know as I've taught them and seen behind the curtain there - even star players aren't dumbasses like people think although many are lazy. The worst are the ones who don't bother to show up (happens more than you think). I've even seen ones who didn't show up for tests (they were on some suicide mission in terms of academics because in the age of the prof/lecturer/GTA turning grades in electronically and directly where they go up instantly for students to see it's harder and harder for ADs to openly cheat without a seriously corrupt system - paper classes like UNC).

However, universities have gotten a lot better about academic support and not cheating (maybe because it's harder to get away with now; maybe because the new support systems have been more successful) and you can tell right away when someone writes a paper for someone else or plagiarizes.

You would be surprised at what those of us who have been there see. It's never who you would 'stereotype' not even in the non-athlete student body. It's never who you suspect. I learned that right away teaching students of all stripes including athletes.