My parents had a very open attitude to alcohol. They weren't big drinkers, but there was always alcohol in the "Drinks Cabinet" and we were allowed to have some if they were having some. So at Christmas etc we could have wine & lemonade or whatever. I never got drunk on a park bench as a teenager, basically, alcohol was no big deal, I'd grown up having tastes and whatever, so I wasn't fussed about drinking as much as I could as soon as my parents weren't there to see me.
My sister has followed the same style of alcohol attitude with her kids, they are now 18 & 20, neither of them drinks to get hammered, my niece even stayed sober on her school prom night because she had dance practice the following day. When having BBQ's etc at her house my sister would buy breezers etc for my niece (there was always beer there for nephew too) from the age of about 14 or so, it has never been taboo or something they weren't "old enough" or "allowed" to do.
I intend to follow the same pattern with my girls as they get older. I already let them taste what ever I am drinking, be it wine, cider or something like a crabbies ginger beer, they are 5 & 8 and generally aren't bothered.
We need to take the buzz out of booze with teenagers. Stop making it such a big deal. The more you throw your hands up in horror and say "NO!!!" the more they will want to do it. Show them what responsible drinking is, lead by example. If they turn up drunk at your house, put them in a cab and send them home. If they bring vodka, put them in a cab and send them home, if they get stupidly drunk on a secret stash, put them in a cab...... Any teen that is drinking sensibly, having fun and not taking the piss, stays. My sister had numerous parties at her house for her kids in the last 5 years, very few of the friends took the piss, as they knew they could drink openly, so didn't binge out of sight.