Project 01 · Series SD
The Shape of the Day
The clock moves at puberty. The bell does not.
Pre-pubertal clockasleep by nine
Adolescent clockthe same sleep, 2h 38m later
0h 00mCircadian phase delay at puberty
—Before the recommended start
The phase delay is measured, by salivary melatonin onset. The sleep windows are drawn to illustrate the mechanism rather than to report a measurement; the recommended start is the American Academy of Pediatrics figure, legislated in California.
Three numbers
The circadian phase delay at puberty, by salivary melatonin onset.State of the Evidence, Ch 4
The start time the American Academy of Pediatrics recommends and California legislated. Most secondary schools start earlier.AAP; California SB 328
Realigning where demanding work sits and how often it recurs uses the schedule the school already has.State of the Evidence, Ch 5
Three levers, graded
Bar width is the weight of the evidence, not the size of the effect. Two will bear a decision now. The third belongs in a pilot.
Start time
Placement and recurrence
Lesson length