I roomed with some Frat Boys a while back, on the whole they were nice enough, but they partied VERY HARD. Not kidding, I didn't know you could fit that many people in a small student house...
It really depends on the fraternity, a lot of frats are extreme party houses, some aren't. Some are very studious and meant for people with high GPAs and academic achievement.
Given that Fraternities are primarily a social thing, I'd advise your son to hang out a bit with the other fraternity members and see how he feels about them, as he'll be seeing a lot of them! If he feels like he really get along well with them, he should go ahead. If, on the other hand, he only mildly enjoys being with them, or only likes one or two other members, I'd reccomend him to give it a pass.