Experiences at uni

This one isn't so much a rant as an actual question to y'all...

It seems I end up in classes all the time that have at least one person who is...what's the PC term these days?.... "mentally disadvantaged"?

I mean that literally, not ironically. In each semester at Concordia so far, I have at least one class in which there is a student who seems to have some sort of impairment, be it down's syndrome or some other actual acknowledged _thing_ that means that they aren't at the same mental level as the rest of the class.

So what I want to know, at the risk of sounding callous and mean, why are they there? They don't seem to understand most of what is going on in class. Prof hands out an assignment and inevitably they'll pipe up with some comment like "But I don't WANT to write a paper!" or worse..."what's a paper?" (that really happened in my AHSC 220 class!). If they aren't at the university level mentally (and each of the 4 people I've had in four different classes haven't seemed to be past primary school, mentally)...why are they there?

Another corollary question -- how did they get in? And what to they hope to get out of it?

Am I the only one who has noticed this? I know Tamara has seen it too, 'cause she is in a class with me this year that has such a person in it.

Kelly? Any experiences with this? Any insights? Can you sell me a clue?