Later start times gave teenagers more sleep — the problem is biology, not motivation
A systematic review of studies that actually changed the school bell
Reviewed by Sian Trombley, CCCFounder, Thrive Family Company
Moderate confidence
Source citation
Minges KE, Redeker NS. (2016). Delayed school start times and adolescent sleep: a systematic review of the experimental evidence. Sleep Medicine Reviews, 28, 86–95. https://doi.org/10.1016/j.smrv.2015.06.002
Published 1 August 2016 · Added to Thrive 1 August 2016 · Reviewed 26 July 2026
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Adolescent sleep timing shifts later at puberty. This review looked at what happened when schools moved to meet it.
Published research findings
The study
Six studies that delayed school start times were reviewed for effects on sleep duration, daytime sleepiness, mood and attendance.
What researchers examined
Whether delaying the start of the school day increased adolescent sleep rather than simply shifting bedtimes later.
What they found
Delayed start times were associated with longer total sleep, less daytime sleepiness, and improvements in mood and attendance. Bedtimes did not drift later enough to cancel the gain.
Thrive editorial interpretation
What this may mean for families
A tired teenager in the morning is usually a mistimed sleep window, not a discipline problem — which changes how the household conversation should sound.
What this doesn't tell us
Important limitations
Few studies, mostly without randomisation, with short follow-up and variable outcome measures. School-level changes also bring other simultaneous changes.
Evidence confidence describes how much weight this study's design can carry — not how strongly the finding applies to any individual child or family.
Therapist perspective — Thrive interpretation, not a finding of the study
Therapist Perspective
Where the bell cannot move, protecting the wind-down hour and the morning light exposure is the version of this families can actually implement.
Practical family considerations
Work with the adolescent clock: fix wake light and wind-down, and stop moralising about mornings.
This research summary is educational and does not replace individualized medical, psychological or therapeutic advice.
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