Nicholson Baker and the plight of math teachers

So, I have just started the Baker article in Harper’s and I’m already pretty annoyed. However, I’m more annoyed (I think) by the reality of the situation than I am by his argument about the situation. We are in day three of school here and one of my jobs as Dept Chair is to sort out math placements for new international and domestic students. I have had the following conversation (or some variant of it) at least three times in the past day and a half:

Student: Why am I in this class? I should be in a higher class, I’ve learned all of this already.

Mr Dardy: Well, your placement test indicated that this was the best combination of challenging you without putting you in a situation where you might fail.

Student: That test? that was unfair, I don’t remember all of that stuff.

So, my question (asked out of frustration) is this – Do other disciplines have the same plague of students not knowing things they claim to have learned already? More importantly, do they deal with some inherent assumption that this is okay to not know what you claim to know? I know I’m not asking anything novel here, but I needed a virtual place to vent a bit so I can continue to smile and deal with my young charges with good cheer.