There are enough people in b-school that don't drink either, or are light drinkers.
Most b-schools are diverse enough that there's usually something for everyone. If you want to get completely wasted, there's compadres that will join you. If you want to just chill and have clean fun, there's plenty of folks that will do that. And there's also a lot of students that will do a mix of both.
Put it this way. Getting absolutely sh*tfaced can be a lot of fun, but it's not like you're missing a whole lot if you don't do it (because if you do, it's not like you or your compadres will remember anything anyways haha). And even though it can be a lot of fun to drink a lot, it usually leads to doing and saying things you'll regret anyhow (speaking from personal experience).
In most social occasions, you always have the option *not* to drink, and in just about every sort of b-school event (whether it's organized or just an informal get together of friends) there's going to be a mix of heavy drinkers, light drinkers, and non-drinkers. Alcohol is really a personal choice. The light drinkers aren't going to think anything about you not drinking, and those who are sh*tfaced won't be in a state to know whether you are or not.
I remember even amongst my b-school friends -- there was a good mix of everyone, from those who did drink a lot to those who didn't drink at all. I highly doubt that those who didn't drink had any more difficulties fitting in than those who did drink. You all go to the same kinds of events, do the same kinds of things (go to dinner, clubs, parties, etc.) so whether you drink or not is really a personal choice.
As for recruiting events, you are best to AVOID drinking at all or drinking just a drink or two at best. Otherwise you risk saying and doing things you'll regret. Some (or in some cases all) of the recruiters themselves will get sloshed (hey, if you were sent on a recruiting trip and the alcohol was paid by the firm, you probably would too!), but that doesn't mean you should. So as a non-drinker this shouldn't be a problem for you at all.
In all, don't worry about being a non-drinker in b-school -- and no one is going to judge you for it as long as you're not overtly judging others for being drinkers.
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