Later School Start Times Linked With Significant Sleep, Daytime Sleepiness Benefits

April 15, 2021
Matthew Gavidia
Matthew Gavidia

Matthew is an associate editor of The American Journal of Managed Care® (AJMC®). He has been working on AJMC® since 2019 after receiving his Bachelor's degree at Rutgers University–New Brunswick in journalism and economics.

Students attending middle school and high school exhibited significantly improved sleep duration and daytime sleepiness with later school start times, while elementary school students were shown to be minimally affected by earlier start times.

Later school start times may significantly benefit middle school and high school students’ sleep duration and symptoms of daytime sleepiness, according to study findings published today in Sleep.

The debate of early school start times has grown in significance in recent years, with a prior study finding that insufficient sleep was associated with impaired behavioral and social well-being, which was shown to affect school performance and physical/mental health.

Moreover, irritability and potential behavioral changes, attention difficulties, and increased risk of migraine were shown to be tied to children and teenagers who experience impaired sleep.

Although American Academy of Pediatrics guidelines recommend that middle and high schools start at 8:30 am or later to align school schedules to a teenager’s natural circadian or biological sleep rhythms, the CDC finds that only 18% of these institutions adhere to this recommendation.

Seeking to further assess the impact of school start times on sleep for elementary school, middle school, and high school students, the present study annually surveyed approximately 28,000 students (grades 3-12) and parents (grades K-12) on students’ typical bedtime and wake time on both weekdays and weekends, as well as students' quality of sleep and their experience of daytime sleepiness before and after 2 years of school start time changes.

In the study, participating middle schools’ start times were set 40 to 60 minutes later and high schools were set 70 minutes later, while elementary schools were set 60 minutes earlier to see if this decrease would have an effect on children.

For the study cohort, slightly more than half were White (55%), with 21% noted to receive free or reduced lunch (FRL).

“Many studies that have looked at the impact of changes to school start times on sleep have focused on school where the majority of students were non-Hispanic White and/or did not qualify for FRL,” noted the researchers. “Both racial minority and low socioeconomic status students at all levels may be disproportionately impacted by early school start time; thus, it is important to consider these variables.

After assessing survey responses, high school students were shown to benefit the most from delayed school start times, as they reported a slightly later average weekday bedtime (14 minutes), but significantly longer sleep duration of 45 minutes per weekday, amounting to an extra 3.8 hours of sleep per week.

Furthermore, more than 1 in 10 (12%) high school students reported improved sleep quality and 1 in 5 reported (21%) less daytime sleepiness. The need for catch-up sleep during the weekend was also improved in high school students, dropping from just over 2 hours to 1.2 hours.

These benefits were also shown for middle schoolers, with delayed school start times associated with significantly longer sleep duration of 29 minutes per weekday, totaling to 2.4 additional hours of sleep per week. An approximate 12% decrease in daytime sleepiness was exhibited in middle school students, with sufficient sleep reported in 21% of these students after the time change.

For elementary school students, earlier school start times had a minimal effect, as this cohort reported an 11 minute decrease in sleep duration. Additionally, the percent of elementary school students reporting sufficient sleep duration, poor sleep quality, or daytime sleepiness did not change.

All results were maintained after a 2-year follow-up, with benefits of later school start times shown to be similar across racial and FRL groups.

“The implementation of healthy school start times (at or after 8:30 am for middle school and high school students) is a critical health policy that can quickly and effectively address significant adolescent sleep debt, with minimal impact on younger students,” said the study authors. “Future studies should examine how early is too early to start school across development.”


Meltzer LJ, Wahlstrom KL, Plog AE, Strand MJ. Changing school start times: impact on sleep in primary and secondary school students. Published online April 15, 2021. Sleep. doi:10.1093/sleep/zsab048