I think it's an acceptable idea. I'd prefer to wait to see how it performs before judging it so harshly like most of you. Especially if the goal is for a safe community.
But...what about diversity? Segregating a certain demographic isn't going to properly conform proper social skills as well as have non LGBT form relationships/break stereotypes/save the world etc.
As if going to a regular high school guaranteed all that for LGBT. And there's always college for the latter.
Edit: mess, this school isn't even LGBT exclusive.