I will disagree with a number of posters on this thread. It is not a 15 (or so) year old boy’s job to choose his environment to be mashpia on others. Of course, wherever he finds himself, he should be as positive an influence as he can be, but he first has to worry about his own growth in ruchniyus, and this impressive young man sees his growth outside of the MO environment he finds himself in.
For those worried about academics (and although I think they’re important, I think at this age the focus should be on a yeshiva which will help him grow in learning). Chofetz Chaim is reputed to have an excellent secular studies department, which they take seriously (as they should).
It’s also probably one of the least “extreme” yeshivos around from the more “yeshivish” type of yeshivos.