film cameras you might consider:
k1000 - clasic student camera. least features of all of them. Tend to be over priced due to their semi-cult status
KM - same as the k1000, but with depth of field preview and timer. often overlooked, and often cost less then the k1000
KX - Same as the KM but with a better meter, mirror lock up, and aperture visable in the viewfinder, as well as shutter speed in the view finder
K2 - like the KX, but no aperture in the view finder, and has the addition of aperture priority auto exposure
ME Super - (not the ME), one of the best view finders ever made. slightly smaller viewfinder then the LX, or the MX. Aperture priority auto mode, shutter speed visable in the view finder, small and light, top speed of 1/2000, metal shutter. shutter speeds controled with up/down buttons.
MX - like a small KX, but more pro features like changeable focus screens. A very popular camera. Also has a semi-cult following. One of the largest view finders.
PZ-1p - a full modern autofocus camera. very similar controls to the K10D/K20D. might be able to find one for under 200.00. maybe.
Also consider K mount Ricoh cameras. I'm not too familiar with them, maybe some one could add a list of their favorites.
I am a big fan of the ME Super. They are cheap, plentiful, and often get sold with a bunch of lenses.
Here is a website with most of the manuals. Have a look and check out the features:
Pentax camera instruction manuals, Pentax professional instruction manuals
Oh, I almost forgot about the Spotmatics. They take screw mount M42 lenses. And Takumars.
You might want to get the camera from a shop that has confirmed it works if you need the camera right away for a class.
Good luck with your class!