Ok, I have to put my two cents in too.
When I was 15 (now 52) a friend of one of my good friends was having a birthday party. This persons parents said that there would be no boys and that they would be there to supervise.
Well there were boys there and beer and her mom was upstairs never ever came down to the basement. Everyone left to go for a ride, the boy that was of drinking age 18 back then was driving and boy was he going fast 100 miles per hour. I admit I was scared. Everyone else seemed to be yelling faster faster.
I guess in my opinion, unless you really know these parents I wouldn't and didn't let my daughter sleep over after a dance.
Yes she was mad at me really angry. But now 25 she has a 9 month old daughter. can't wait to see what they will do when she wants to stay over after a dance.
A lot of parents out there don't have limits.
Follow your gut.