Our district went to later starts for middle and high school about five years ago. There's lots of evidence that it improves attendance an test scores, lowers truancy and behavior issues. Side effect for home life is that with less unsupervised time it also appears to lower pregnancy rates in some communities.
My kids aren't to high school yet, though my oldest is in middle school. So my kids have not moved to later rising. They both are up with th birds, and always have been. I've had people suggest I keep them up later so they would sleep later, but that never worked. They might sleep 30 minutes longer if kept up several hours late, but they would also be cranky and emotionally fragile. They really need a solid 9-10 hours of sleep most nights; when they get up at 6am, that means bed between 8 and 9, ideally. And that's for upper elementary. Through about 2nd grade, they did best with 8pm as the latest time we would aim for.
While I know that averages are averages and every kid is different, I suspect that there are huge numbers of children who are very, very sleep deprived, most of whom have parents who say "well, my kid is different! S/he just doesn't need much sleep at all!". Then they usually list a bunch of behavioral symptoms of sleep deficit and call them evidence that the kid doesn't need or want to sleep.
Given the growing body of evidence on the role of sleep in hormone production, particularly growth and appetite control hormones, I wonder what role chronic sleep deprivation has in things like the rise of childhood obesity, diabetes, etc.
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