CTY asks that kids take the US college test, called the SAT. I don't know if SAT is given in French, but there is a section only with Math, and if your child qualifies in Math he can take Math and many Science classes. They would be in English, but I would give it a try anyway. About a third of the kids at my son's CTY site are from overseas, by my son's estimate.
First thing to do is to look at the College Board site and get the testing started.
(I've put my son on an airplane to go to camp at age 12. If you can afford it, it's fine.)
Enjoy,
Grinity
