This is one reason admission selectivity matters. Top colleges tend to be selective. They also tend to have relatively small class sizes, on average. Small classes + selective admissions = discussions that aren’t dominated by dumb (/unmotivated) students. Ideally.
That doesn’t necessarily mean they are all good discussions. Discussion may get dominated by students who aren’t stupid, but who bloviate. Imagine a young Donald Trump in your first year Greek Thought & Literature class. A good instructor will insist that he stay on topic, support his arguments with evidence, express them coherently, and respect other students. It may take an instructor with more experience than the average TA to manage a young DT. This is the kind of learning experience he evidently missed as a transfer student at Wharton.
However, the selection process commonly includes other factors besides those predictive of academic strength.
Seems like those who are dumb and motivated could waste a lot of time, since those who are dumb and unmotivated may just passively not understand what is happening in class (or miss class much of the time).
Even in a small LAC with generally small classes, there will be some large survey classes, particularly in lower level science and history classes. Some of these may be distribution requirements.
“The whole idea of anonymity in large lectures is odd. Why is it good to be anonymous? I get the whole deal with missing a class because you stayed out to late or couldn’t focus because you were hungover. Been there done that. When kids talk about missing classes like it’s a badge of honor, I have to ask myself why are they there? That happens less when there is a small intimate setting involved. People actually care if you show up. That’s part of the maturing process in college. Making good decisions. Perhaps for the first time in many students lives, their actions actually have consequences.”
There are cultures where being anonymous is preferred.