As others have pointed out, A*Men is very youthful - I think of it as a "clubbing" scent, both in the sense that one might wear it out to a loud and noisy club and in the fact that it is potent and can overwhelm.
My own instinct here is that people in high school tend to "over apply" almost everything, from make up to fragrance, and this is one that could be a problem if he went even one spray too many. It's very tenacious and projects. If it gets over applied, the only solution is a shower and a change of clothes. It clings to clothes for days.
While its perfectly suitable to wear out to the mall with friends, I'd probably recommend something a bit less bombastic for school. Gendarme, Mugler Cologne, or (my high school mainstay) the soapy green "Grey Flannel" might be better for day-to-day wear in the crowded confines of high school.
If he absolutely has his heart set A*Men, perhaps he should start with the aftershave tonic, which should be by its very nature far less tenacious and aggressive but would smell essentially the same.
- - - Updated - - -
Actually one other thought.
Mugler launched a summer flanker a couple of years ago called Angel Men Sunessence Orage D Ete . It has since been discontinued but can still be found on the internet and eBay. This was designed to carry the "spirit" of A*Men, but without the overbearing qualities that would make it a poor choice for summer. This might make a great alternative for school. It's much lighter, has a bit of a citrus start, and then settles into a brighter, lighter version of the original.
A*Men is built for cool nights. Sunessence is the same idea built for daytime wear (or at least as "daytime" as A*Men can be...)