MIT undergrad is ridiculously competitive. I'm sure you've heard it all already, but there are many perfect SAT/ACT, 4.0 high school students who do not make it into MIT, and I'm not really convinced it's a bad thing. I think it's easier to differentiate yourself in college and you can go to a top level grad school much more easily than in undergrad.
I guess what I'm saying is I hope he understand that this gives him a solid shot, but he should also realize that not getting into MIT is in no way a statement about his potential. There are some high schools that churn out MIT students though. If there are many people in his school going there he has a much better chance it appears.
Those sound like really boring schools though, guess you gave him the old HH treatment proper. Just kidding, I've met a lot of MIT people in grad school and most of them are as cool as you could expect for someone from MIT