It's great that your son is going to learn basic 35mm photography. I'm sure it will be very enlightening for him!
A couple points though:
1--Your bias to Canon is not very useful because Canon has never made a 100% mechanical student camera in the EF mount. They only made them in FD and FD is not compatible with your digital Canon so there's no valid reason to lock your son into your favourite camera brand. You could buy him a 35mm Rebel if you want to be able to swap lenses but these cameras are more complicated than necessary for basic photography and, in my opinion, result in confusion and dependence on auto features instead of concentration on the true basics.
2--Do not listen to these people who suggest you can buy a 35mm SLR for under $100 on Craigslist or wherever non-camera retailer. This is a gift for your son and he needs it to earn a good grade and to educate himself about photography. Therefore you should buy from a camera store. You can buy a new Nikon FM10 or Vivitar 3800n from BHPhoto.com or Adorama.com for less than $400. You can buy a used, higher quality 100% mechanical SLR like a Nikon FM, FM2n, F2, F3, Canon FTb, Canon F-1, or Pentax K1000 and lens for less than $400.
3--Whatever camera you buy him, instead of focusing on brand, focus on what lens/es you buy! This is FAR more important. Whatever camera body you buy, buy a 50mm lens. It can be an f2, f1.2 or anything in between, but 50mm lenses are crucial to the 35mm film photographer. Do not waste your money buying a bunch of zoom lenses. They are not useful for learning basic photography on because DoF is more difficult to understand with them. A typical 35mm SLR kit consists of a 28mm, 50mm and 85, 100 or 135mm. If you buy a cheaper camera like the Canon FTb, you could spend your extra money on a couple good lenses in these lengths. A new Nikon FM10 or higher quality FM2n, F2 or F3 with a 50mm 1.8 or 1.4 will cost most of your budget. It's up to you as to if you think he'll benefit more by a simple higher quality camera or a cheaper one with more lenses. Don't forget there will be film, processing and printing costs on the way too! You may want to set aside $150 or so for a couple months worth of film. Find out what brand/type the teacher wants them to use and buy it cheap at BHPhoto.com or Adorama.com.
4--It may sound like I'm suggesting a lot of Nikons and this may not appeal to you as a Canon shooter but most film shooters will tell you that Nikon is more popular among us because 1.) They still actually make film cameras and Canon stopped years ago and b.) They made many more 100% manual film cameras which are preferred by most film shooters and Canon stopped making those years ago too. Canon's a great company but I feel that buying Canon 35mm cameras now can put a photographer in a bit of a limbo situation. Either the lenses cannot be used on new DSLR's or you can't get the exciting, disciplined full manual film experience. You can do both of these with Nikon and Pentax.
Good luck with your shopping! I encourage you to look for a local used camera shop too and see if your son has any preference. Whatever camera he is most inspired by will be the one he'll use and enjoy the most!
MANUAL AND METAL! FILM FOREVER!