Hmm, interesting. I only have my own experience to draw upon. I have never taught anyone how to take photographs, or use a camera particularly but suppose you do have a few options.
As suggested above you could get something like the EOS-5 (A2E) which will be a solid (if somewhat odd looking!) high-quality film camera with both manual and automatic options. My only concern is, I suppose, that you could easily just leave the camera in automatic and so not really learn about aperture and shutter speed, and metering etc. But equally, you might find the array of options really helps you and draws you in. Excellent all-round camera though.
I myself started with a Pentax ME, which at least gets you into thinking about shutter and aperture because you have at least to turn the aperture ring and read the shutter speed. Oh, and focus too. Any AE or manual SLR would do, and these are also cheap now. As a starting point almost any of them would do, and some of the pentax/OM olympus/FD canon are now very cheap for exceptional potential.
The third option is to start with digital, and by their nature there are no nikon FM/Pentax K1000 style digital cameras. They all have automatic settings, and some (all SLRs) have manual settings too. You could learn with one of these, and you do get instant feedback. Because the shots are so easy-come easy-go it is all too easy to just snap away without really thinking about the photograph, and it's the thinking which makes you learn.
Bottom line:
What's right for you depends on your aims, your budget and your will. You can learn with anything, some tools make it a bit easier. Maybe you already have, or know someone who has, a disused film SLR you could fool around on?
People are right, film does cost money, but I've worked out how much money I would spend on film (even at today's prices) plus how much I would spend on film gear, and the comparable digital equipment costs, and there's not that much in it (mainly because I know I take less photographs when I use film, I'm not sure more photographs always means more learning). Plus I've got real slides (or negatives/prints) to look at. For every shot!
[In the UK it's possible to get the Pentax K100 D Super for only £220 with the lens, if I was buying again, I'd get one of those - so cheap!]