I'm consistently amazed by friends/family who put their kids to bed well before 9pm (even as early as 7:30-8pm). I don't think I've been able to get to sleep before 2am or so regularly since I was very young... Even if I force myself up at 7-8am, I'm still up until 2-3am most days.
On either saturday and/or sunday I'll let myself sleep until I wake up (usually 12noon-2pm). I'm fortunate enough that my first morning meeting is 9:30, and it takes about half an hour commute. My alarm starts at 7:15, and I usually snooze until around 8... it takes me nearly an hour to get going once up, and even then, I'm usually walking in the door just as standup is starting.
I'm amazed by the early-start types, as I've tried... It only made me really tired and funny for a few days, then increasingly grumpy. At 19, I worked two jobs, first at 4:30am, and second ending around midnight... I was a really grumpy young man by the end of that month (quit one of the jobs, just couldn't keep up with both).
Then I managed to find a job doing creatives/design, and fell into programming from that. All the same, in a lot of places "office hours" have been the biggest contention in the workplace for me. I get things done, I have high quality output, and significantly so.
Have you ever gone camping for an extended time (week or two)? Real camping, where you don't have access to any screens, and filled with daytime activities (such as fishing or hiking)? If so do you still end up wanting to stay up till past midnight, and sleep till noon?
I've found that if there are no major artificial light sources, and if I've been outdoors active all day, I tend to want to fall asleep soon as its dark. And I wake up way earlier, soon as the daylight starts to hit the tent.
Importantly, the same research that indicates that kids would do better starting later also indicates that they (teenagers, at least, who were also the indicated population in the study about later start benefits) will generally have trouble getting to sleep much before midnight, regardless of when you 'send' them to sleep.
I still am not one of the accursed 'morning people'.
Maybe it's natural for /you/ to get up that early, but it never was for me (the closest I came was waking up super early for reruns of Mr. Wizard, then falling back asleep).
More constructively phrased: make them run around outside a bunch during the day, and don't let them use devices with screens after dark.
Works for adults, too (especially if you also reduce use of artificial lighting) though it can be a struggle to fit that into modern life—especially in the Winter, since kids don't do much running around at school these days and it's dark shortly after they get home.
As a parent, I can state that getting lots of exercise is very useful in persuading kids to go to sleep at a reasonable hour. It's not bad for the parents, either.