My daughters are almost 16 and recently attended a friend's Halloween party. Apparently, there was an after-party 'co-ed' sleepover, and when one of them hinted she'd like to stay, I refused.
I then explained to all of them that, where I come from, some things just aren't done.
Good for you!
I had a 13th birthday sleepover. Boys came to the party early and were required to leave at 8. Period.