> And around puberty, their circadian clocks shift by a couple of hours, meaning they get tired later at night than before and wake up later in the morning than

> And around puberty, their circadian clocks shift by a couple of hours, meaning they get tired later at night than before and wake up later in the morning than they used to. This shift reverses at adulthood. The biological nature of this daily rhythm means that sending a teenager to bed earlier won’t necessarily mean they fall asleep earlier. It's not clear to me that this shift is actually biological in nature, or trained in from years of habit. I still have friends who never got jobs or careers after high school. Now into their 30s they are staying up regularly to 3-4am. If anything, their circadian rhythm has further extended. If this is the case, "letting teenagers sleep in" might just offset that habit correction into the college years, or the early career years, or etc. Or constitute a permanent change in circadian rhythm for that generation.