Oxford University: Teens are fully awake and engaged at 10am

The neuroscientists at the University of Oxford are diving into the research on adolescent sleep. This video gives a brief introduction to the topic. The scientists write:
Is sleep different for teenagers? The reason we are so interested in sleep during adolescence is because our circadian rhythms change during this period. From the age of 10 until around 21 our circadian rhythms delay. This means that as we go through adolescence and into early adulthood we are naturally more inclined to go to bed later and also to get up later. This is a biological process, and will happen to teenagers regardless of their environment.
Asking an adolescent to get up at 07:00 to start school at 09:00 is akin to asking a 55-year-old to get up at 05:00: this leads adolescence to accumulate a significant amount of sleep deprivation. The circadian drive isn’t optimised for wakefulness and engagement until around 10:00. This means that adolescents are typically starting school at a time when they are feeling the effects of sleep deprivation and when their natural rhythms are not optimised for alertness, and therefore learning. There have been a whole host of studies, mostly from the US showing that a delay in the school start time improves sleep, mood, well-being, alertness and academic outcomes with one study suggesting that a delay in the school start time is more effective than improving the quality of the teaching.