I think that most (if not all) of the study abroad programs out there don't really let you choose the region of your country (at least it's not guarantee). But your son should be able to get France in general. I think EF Foundation is good/OK, but definitely stay away from TWU (
http://www.askmehelpdesk.com/study-a...ed-36786.html). Other good, reputable programs are Ayusa/Intrax, AIFS, ASSE, AFS, CIEE, and YFU. Check out the websites, compare prices/packages, call them up and figure out which you are most comfortable with. Sometimes different programs are better in certain countries. There is also Rotary Youth Exchange, where you only pay about $1000, but there's no guarantee you'll get your first choice country.
A good forum/website to look at is
http://www.cultures-shocked.net/ , which has lots of people that know about high school exchange. Try posing your question over there and you'll get lots of answers.