There is no clear association between later school start times and student academic outcomes, as two studies reported significant positive associations (b = 1.78, b = 0.98; effect sizes could not be calculated from one study), one study reported a non‐significant negative association (b = −0.02), and one study reported a significant negative association (MD −0.32 GPA points on a scale of 0 to 4, with higher GPAs indicating better grades).

254,743

(4)

All studies that evaluated the association between later school start times and amount or quality of sleep reported significant positive associations, providing evidence that later school start times are associated with increased sleep (effect sizes ranged from MD 0.49 to 1.95 hours) and lower risk of losing sleep (RR 0.41).

52,340

(8)

There is limited evidence concerning the association between later school start times and mental health outcomes: one study reported significant differences in self‐reported depression symptoms for students in later starting schools (07:25 and 08:30) than earlier starting schools (07:15), but no significant difference between students starting school at 08:30 vs 07:25.

1200

(1)

There is mixed evidence concerning the association between later school starts and attendance outcomes: one study reported a significant increase in attendance, one study reported a non‐significant increase in attendance, and one study reported a significant increase in attendance for 2 of 6 schools and non‐significant effects (no further information provided) for the other 4 schools.

255,122

(4)

There is mixed evidence concerning the association between later school starts and student reports of alertness or sleepiness. Two studies found an association between later school start times and decreased daytime sleepiness, while one study found no difference between student reports at later and earlier starting schools. One study reported a significant increase in attention levels but a non‐significant increase in concentration levels.

2735

(4)

Authors provided limited information concerning adverse events and unintended consequences but did offer that later school start times may be associated with decreased morning interactions between parents and children, decreased alertness in mid‐afternoon, and increased logistical challenges, including missing extracurricular activities, transportation troubles, and safety concerns (as students may have to walk home in the dark).

207,576

(4)