First, I should commend you in taking an active role in your son's education/plans.
It's definitely true that no one will EVER care about where (and even if) you got your degree, and what it was in. It's been said here before, and I'll say it again:'the filmmaker makes the film, not the film school'.
With that being said, the film school does serve a purpose with (hopefully) offering connections and screenings to the industry, decent enough equipment. Mostly though, it has a creative atmosphere with like minded people.
I'm mostly familiar with grad programs, and others will correct me for sure, but I think out of the 'top' (an arguable term, but generally accepted) schools, AFI & Northwestern University are the only schools that are Graduate level only.
Off the top of my head, decent undergrad programs are at NYU, UCLA, USC, UTexas, Columbia University, Florida etc...
Personally, I think places like Full Sail, New York Film Academy, Pittsburgh Filmakers etc... are a complete waste of money/time. People will point and say "but so and so went there!". I've known a few people that have gone there, and most have said they are not worth it. If you can't get into a decent program, then think of it as an alternative. Last Resort.
At the end of the day, I think your son is still really young (he's just graduating high school), and needs to have crazy experiences, incredible realizations, and an education on which he can draw upon that will set him and his stories apart from his peers (there are A LOT of peers). Thus, I'd suggest going to a college/university. It is entirely true that he doesn't *need* to go to become a great filmmaker. However, I think he will be a better person for it. Also, it will give him something else to fall back on if it doesn't work out. Probably not what you/he want to hear, but true.
If you haven't already, take a look at the following links, which I found useful when looking at schools:
http://www.tomedgar.com/fsc/
Film School Confidential: A great, warts and all look at schools and what to expect. It's geared more for the grad level, but I think the knowledge in there is very sobering. I'd definitely read the 'Before you Go' section.
http://filmmaker.com/reviews.html
LOAFS...reviews from students of schools. A lot of them are borne out of anger and bitterness, so beware.