One of the Science Bloggers I find myself reading more often than many others has written some posts concerning sleep. This isn't a subject I'd ever really given a lot of thought, especially as he relates it to school performance as well as general safety issues. Read his blog posts that got me thinking here and here.
I won't even approach his scientific discussion beyond mentioning that humans go through phases in regards to their sleep, happening loosely around adolescence, teen (high school) years and then adulthood, around 30 years old, at which point we settle into our adult sleep patterns. From reading his posts, I would say I'm an owl in that I tend to fall asleep and wake up later. I'd always assumed this was due to jobs I'd chosen, but perhaps it's more that I chose jobs that corresponded with my basic circadian rhythm. Working in restaurants I've always felt that, in the end, it's the business that does the picking, but that's another post. In addition to owls there are also larks, people who tend to fall asleep and wake up earlier, and what he calls the median, self explanatory in meaning. I remember years of thinking that I didn't sleep because I would toss and turn in bed for hours before getting to sleep. I was also difficult to wake up in time for school.
I certainly believe that school starts too early. If I were creating a public school system, early mornings would certainly be out from the very beginning. I would say honestly that a part of our homeschooling decision was based on the timing in general of school, from the early mornings to the forced late nights. The early start certainly wasn't a huge factor in the decision, so perhaps it's more a huge residual benefit.