First question to answer is how responsible is this 12 year old daredevil kid? That can be a starting point for the type of camera you select.
Is he the one that wants to learn the manual aspects or is it you who want him to learn those aspects? Is this for a class or fun for him? Sort those kinds of questions out first.
Then I would start at the lowest cost you can find for a camera and go digital..You can check with a good camera shop and maybe find a second hand camera...but beware there are lenses etc that can be had and changing lenses is something that must be done carefully. Personally I shoot with Nikons ( I have several and professional level cameras) but my cousin a professional, shoots with Canon and both are very good. I would not get the most expensive one at the outset. Our daughter got her son a Nikon D80 a few years ago for her son and he did not take care of it, ended up using hers and he broke that one too..
Good questions. He's responsible enough to make sure he doesn't lose the camera, but not enough to accurately judge how dangerous a situation is. He WILL misjudge situations and the camera will likely be dropped. It's part of the reason I've held off getting him a real camera even though he's wanted one for 5+ years.
He wants to learn to take photos, and given his personality he will soon want to know more about how and why photography works. We've looked at the science behind a pinhole camera, lenses, the human eye, and the shutter on a camera including how to stop motion and adjust for depth of field and the subject definitely interests him. Also, it's part of our homeschooling for this spring/summer with tie-ins to art and physics. I've found a class at a local camera store that will cover more depth than we've done so far.
Thanks for your input. Your questions have helped me flesh out more of what I'm looking for.