Not abnormal, maybe a bad choice of phrasing there. Rather that during puberty people need more sleep and their rhythm shifts forward. This is exacerbated by po

Not abnormal, maybe a bad choice of phrasing there. Rather that during puberty people need more sleep and their rhythm shifts forward. This is exacerbated by poor sleep hygiene (eg screen use), but in general teenagers get tired later on than their parents. Hence suggesting that kids will just stay up later is missing the point. The stereotype that kids stay up late partially arises becuase they have shifted circadian rhythms and they can't help it, not that they want to take advantage of later school starts. And so the benefits of later starts are important becuase it more naturally fits with teenage sleep patterns. For more info: https://www.ncbi.nlm.nih.gov/m/pubmed/19546564/ https://www.ncbi.nlm.nih.gov/m/pubmed/19546564/ > Adolescents continue to show a delayed circadian (or internal clock) phase as indicated by daily endocrine rhythms even after several weeks of regulated schedules that allow for sufficient sleep. This delay is maintained under controlled laboratory conditions in which there is limited possibility for social influence