Curry parents, I've been there. Didn't even ask if I was allowed to go to Schoolies - my parents and my sister would have been like NO. Having said that, Schoolies wasn't really my scene anyway. Probably because of my upbringing, I was never...used to that kind of environment.
However, could you compromise with your parents? Perhaps if you could organise something else with your friends - some kind of other trip, instead of Schoolies? This way it's with kids your parents MAY be able to trust (if they know your friends that is) and you are less likely to experience the shenanigans?
I'll be honest...I personally am not a fan of Schoolies and I would strongly discourage my kids from going. On the other hand though, I wouldn't mind if my kids (having just finished year 12) were to go with a few trusted friends whom I know are decent people to travel and the like.