The one big exception I can think of is the arts. But they usually require an audition or portfolio for acceptance. CS majors take anyone but then not until first week of classes is it clear how much pre-reqs are expected.
[EDIT] incidentally, the arts are also infamous for being dominated, at a professional level, by kids with artist parents and kids with rich parents (who can bankroll years of private lessons and then years of little-to-no income while paying for access to career-makers) so... there's that.
Of the 22 people in the class, 21 of them were singers - everyone except me. Much of the class was around singing - singing scales, etc. I saw nothing in the syllabus that required singing, but... you had to learn to sing stuff by sight reading, and... I'm not a singer. It was embarrassing for me (and probably for others). I think I managed to drop out before losing all my money on that, but... frustrating. Could also tell most of these people had had voice lessons for years, and were all taking this class as a way of getting in to theater work, not... to play an instrument.