How a fixed early and late school start schedule affects sleep and daily rhythms in teenagers of different ages

1,969 Mexican adolescents reported distinct sleep patterns based on school shift schedules.

• Afternoon shift students had later bedtimes, rise times, and midpoints of sleep compared to morning shift students.
• Afternoon shift students experienced less social jetlag and had longer time in bed on school days.
• The peak lateness of chronotype for afternoon shift students occurred at age 15, while morning shift students peaked at age 20.
• Girls in the afternoon shift peaked at age 14 for chronotype lateness, while boys peaked at age 15.
• Adolescents in delayed school start times reported adequate sleep compared to those in fixed morning schedules.
• The findings suggest that school start times may influence the peak of late chronotype.

Simplified