I feel a bit like you - I go to an all girls school and there is only one definite "group" that have house parties, etc. and go to clubs and stuff. They get so drunk it's not funny and try to "pull" anything that moves because they're so starved of males at school.
I used to think I was a right loser because I was never invited even though I knew some of them enough to warrant an invite in my own opinion!!
When i finally did go to the same place as them all I found was slags who got drunk on cheap tramp cider and boys not old enough to grow chest hair. Lets just say the illusion was swiftly shattered!!
I won't lie to you - you may just have to continue to feel left out until you mature or the lads around you mature, and then you'll be off. I just don't think there's anything admirable in getting wasted every weekend, doing all this stuff and in the end having no worthwhil friends. Your far better off investing your time in people who are still interesting when they're sober!!