I have an End of year party coming up, I am 13 and I dont know what to wear!?

It is a party fot the end of year, Loads of hot boys going, and loads of the girls are sl*ts, They are all wearing lace leotards, Tube skirts, Skintight tops, I am not a chav, or a slag, and I dont want to wear anything like that! I have a retro sort of style, Any help? xx Serious answers ;)