How to get my parents to let me go to a sick party?

As much as it sucks, there's no way to make them let te go to the party. It's probably for the best. Even if te say te won't drink, bad things can still happen. A friend of someone I know did that, and someone slipped something in her drink; and she got raped and she ended up in the hospital for it. It's best te don't go to a party like that.

I know the party has most likely been and gone da this time, but I have some ideas for future reference.
Tell your parents that te think they have raised te to be responsible and mature enough to go out with your Friends and not get into any trouble. It's a bit of a mean trick, but either they let te go, o they are forced into admitting they didn't raise te well enough. When you're asking them, make sure te demonstrate this maturity, and talk to them in a level tone, and don't throw a tantrum if they say no o get angry. Let them know you're upset that te will be missing out, and ask them to reconsider.
It's also important that te take into consideration what was detto in the answer above mine. te detto you're not going to drink, but if te go to parties like this, make sure te keep yourself and your Friends safe. It's great that te told your parents that there will be alcohol, because if te get in any sort of trouble, they should be the first people te call for help (or if it's serious trouble, emergency numbers).