I also have a 14 year old and you just can't. DD will stay up nearly all night when she has sleepovers, so I discourage them as much as I can. Instead, I take her and her friends to evening events and drop off after, or they hang out at each other's house and I pick her up/drop them off at 10. They don't seem to mind it too much, as long as they get to stay out until 9 or 10, and DD isn't nearly as grumpy the next day.