From the onset of puberty
until late teen years, the brain chemical melatonin, which is responsible
for sleepiness, is secreted from approximately 11 p.m. until approximately 8
a.m., nine hours later.
Here is an article is about a teenager who kept a digital diary of her school days. She regularly gets only 6 hours of sleep a night- 2/3 of how much sleep she should be getting in order to be fully functional.
I don't have any experience taking any of these classes but I would love to take one (just to try it) in the future. More people would definitely be interested in taking the MOOCs classes if it was available for credit- but I guess that would put a lot of the private institutions out of business. In my opinion, flexibility would be MOOC's key to success.