What if one of the reasons so many teenagers are unpleasant to be around is because most of them are chronically sleep deprived?
...87 percent of high school students are chronically sleep-deprived, and such regular sleep deprivation is putting our children at greater risk of depression, anxiety and obesity, as well as fatigue-related accidents and injuries. (source)
Usually, any complaints about the cruelty of getting teenagers up at 6:30am to get to school for a 7:45 am start time are met with a "Well, they need to learn how to get up early. It's part of being an adult!" But our experience has been far different from what most would expect.
We let our teen sleep until she wakes up. And we let her set her own bedtime, too. When she first started staying up late (that is, turning her lights back on and doing stuff in her room after official bedtime) she did indeed pull some nights where she didn't go to bed until midnight or 1 am. That didn't last very long, though, because she discovered she didn't like being super tired the next day or nor did she like sleeping till noon and losing half the day. After a couple of weeks, she, on her own, set her bedtime at 11pm. For about half a year following that, she slept until about 10am. (That's 11 hours a night, on the generous side of the 8-10 hours of sleep recommended for teens by the National Sleep Foundation.) Since the switch to Daylight Savings Time, she's been getting up around 9 am, for a total of 10 hours of sleep a night.
Now, conventional wisdom would dictate that because she's used to sleeping until 9 am, it'd be pretty impossible to get her out of bed on the occasions when we really must be out the door for something early in the day. But this has not been the case. In fact, she has absolutely no trouble occasionally getting up at 8 am or even 6:30 am. She's sleepy, sure, but she can do it, and do it without us physically dragging her out of bed or without multiple wake up calls and without her being super grumpy or crabby.
I'm convinced this is because she's not chronically sleep-deprived, like almost all teens are. She gets enough sleep, and so can tolerate an occasional early morning. When she'd done growing and she's reached full adulthood, she'll transition to an earlier waking time. Or, if she can't do so naturally, she'll have the impetus of a boss and a paycheck to motivate her to do so.
The list of effects of teen sleep deprivation is pretty sobering, although that article suggests (wrongly, I believe) that parents insisting on an early bedtime as a solution. Teens usually can't fall asleep earlier. I think the answer is a later start for schools. Much later.