I think it depends what kind of school you have. Like dress codes.
You could ask your friends. Though, if you don't want anyone to put the pressure and ask questions like "You've never been to a spring fling dance before?"
Well, you should just say something during a conversation like,
"So, have you figured out what you are wearing to the spring fling dance?" Usually people, mostly girls, like to talk about this. So, I think it will be easy for you to get information.