You get booted after getting a certain number of demerits, and I suppose if she lied about drinking and got away with it, then he'd have gotten more demos for the drinking. that might have been enough to put him over the top.
But again, that's just speculation. You need details before reaching a conclusion.
My husband is a '73 grad. He said it was a big mistake whenthey allowed women. Looks like he is right.