I've been to (and hosted) a few co-ed sleepovers, my first was when I was 17.
I've never been to one where people were doing anything 'bad', the group I hang around with usually just play games/talk/eat/whatever. No weird sexual things lol
I don't see an issue with co-ed sleepovers/overnight parties.
I've stayed overnight after plenty of parties....it's better than drinking and driving.
I also had a few friends in HS whose houses were always open for a party...the parents just didn't care if you drank/smoked/whatever in the house--even if they were or weren't home.
I find that weird! And the guy whose house it was is a total deadbeat now....so ya...i think that was certainly bad parenting.
same