Certainly Blansky's offer of a free Nikon will be hard to beat, but my comment is that the Pentax K1000, although not ridiculously overpriced, is still pricier on the used market than many similar cameras from less prestigious brands. Ricoh's already been mentioned, but Chinon, Cosina, and Vivitar all made (or at least sold) K-mount cameras that are perfectly serviceable for this function. Sears-branded cameras were, IIRC, made by Ricoh. I've got an all-manual Vivitar V3800N that would probably do quite well for a student camera. I forgot what I paid for it, but it was peanuts on eBay and in like-new condition. Even a Zenit 122K or 212K would do nicely, provided it's a working sample. My other K-mount cameras all have auto-exposure modes. My personal favorite is the Chinon CE-4s, since it's got some handy convenience items like a film box-end holder and a little window to show you the selected aperture in the viewfinder. (Sadly, my CE-4s's meter is a bit flaky.) Among the ones I own, the CE-4s and the Pentax P30t would both make good student cameras, provided the student can be trusted to resist the temptation of using the aperture-priority auto-exposure mode.
I've mentioned K-mount cameras simply because I'm familiar with them but also because what I assume to be the popularity of the K1000 among students means that a student who picks a K-mount camera stands a good chance of being able to share lenses with other students. Expanding out of the K-mount world, I'm sure there are lots of other possibilities, but I'm less familiar with these cameras.