The daily sleep cycle tends to move late for teens (they tend to sleep later and wake up later).

The American Academy of Pediatrics has been recommending later school start times (no earlier than 8:30 am) since 2014.

The early/late school start time has been linked to grades (4.5% increase in the median grades; see Dunster2018sleepmore), attendance, graduation, injuries for athletes, crashes, anxiety, and suicidality.