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School Start Times and Sleep

According to a survey by the National Sleep Foundation, 60% of teenagers report feeling tired during the day, and 15% have fallen asleep at school.

Sleep-deprived kids are more likely to suffer academically, be overweight, display symptoms of depression, and engage in risky behaviors like drinking, smoking, and using drugs.

Clearly, poor sleep is bad for students. Fortunately, the American Academy of Sleep Medicine, the American Academy of Pediatrics, and a wide host of academic researchers, parents, and other advocacy groups have identified a potential fix: changing school start times to 8:30 am or later.

Unfortunately, 93% of high schools and 83% of middle schools start before 8:30am, according to the CDC.

Could later school start times be the solution for healthier, happier students? An ever-growing body of research says yes.

Below we review the dangers of sleep deprivation for students, and why the unique sleep needs of adolescents are a key consideration in delaying school start times. Then we take a look at the major studies supporting a change in school start times.  

Sleep deprivation and students

Given that 90% of students don’t get their recommended 9 hours of sleep on school nights, it’s no wonder students are so exhausted.

With increasing responsibilities from work, school, and extracurriculars, students simply don’t have time for sleep. Making matters worse, many adolescents and parents are unaware of how certain behaviors they engage in, such as using electronics at night, actually reduce the quality of the sleep they do get.

Sleep deprivation isn’t something to take casually. It’s serious for all of us, and more so for teenagers.

Whenever we’re sleep deprived, even it’s just from one night of poor sleep, our cognitive functioning suffers. That includes our ability to concentrate, our ability to retain or remember information, and our ability to problem-solve. These skills are all required to perform well academically.

Sleep deprivation affects us emotionally, too. Sleep-deprived people are more likely to make poor judgments, act irrationally, or have difficulty regulating their mood or impulses. For teenagers whose hormones are already going haywire, these effects are only worsened. It can cause them to engage in substance abuse, have trouble coping with the stress of school and social life, and think they’re okay to drive when they’re really too tired. Car accidents are the leading cause of death for teens.

Finally, sleep deprivation has physical consequences, too. When we don’t get enough sleep, our body produces more of the ghrelin hormone, which craves sugary and fatty foods, and less of leptin, our appetite-regulating hormone. Sleep deprivation can lead to weight gain, or simply fueling yourself with the wrong kind of food – making you even more tired. Chronic sleep deprivation is also a risk factor for type 2 diabetes, heart disease, and certain types of cancer.

Sleep deprivation can negatively impact teens – mentally, emotionally, and physically. But do school start times really have such a large effect on adolescents, and if so, why? Next we’ll review the unique sleep pressures placed on adolescents, as well as the research-backed benefits to enforcing later school start times.

Unique sleep needs of adolescents

Longer sleep and changing circadian rhythms

One large reason students are so sleep-deprived is that they need more sleep than the rest of us, but they have no time to get it. Teenagers actually need 9 hours of sleep per night, as opposed to the 7 to 8 hours recommended for adults.

Also, right around adolescence, children experience a natural circadian shift, where their body and mind become tired at a later time of day than when they were younger. Their brain begins melatonin production (the sleep hormone) later in the evening, and stops production later in the morning. As a result, they naturally feel ready to fall asleep and wake up later. Unfortunately, this corresponds with the time they often start going to school earlier.

Increased time demands

School start times are a big deal because in large part, they dictate the way adolescents live their lives. Start times are non-negotiable and unyielding. As such, students have to find ways to fit in everything else they’re responsible for outside of school.

That includes homework, extracurricular activities, family obligations, jobs, hobbies or leisure time with friends, and basic needs like eating and bathing. These demands have only increased as colleges and career opportunities become more competitive.

" I sat in the living room in our house on the ground, crying and having horrible breathing problems. It was so scary. I think it was from the accumulated stress, the fear over my grades, the lack of sleep and the crushing sense of responsibility. High school is a very hard place to be. "

- Chloe Mauvais, sleep-deprived high school senior

Sleep hygiene issues

Complicating matters is the poor sleep hygiene many adolescents unknowingly practice. Sleep hygiene refers to the thoughts, behaviors, and habits we have around sleep (similar to how your oral hygiene affects your dental health).

Among other things, the basics of good sleep hygiene include:

As any parent of an adolescent can attest, many teenagers do not adhere to these ideals, and often through no fault of their own. They drink a lot of caffeine or energy drinks in order to keep up with their responsibilities, trying to avoid exhaustion from running on such low sleep. They sleep in on the weekends, causing a sleep hangover effect come Monday morning. After hours of homework, they finally go to bed with their smartphones, where the blue light from the device tricks their brain into thinking it’s daytime and keeps them awake.

" It’s nice to stay up and talk to your friends or watch a funny YouTube video. There are plenty of online distractions. "

- Carolyn Walworth, sleep-deprived high school senior

Many of our habits continue into adulthood, where these same poor sleep hygiene practices continue to cause problems. Many of us are simply unaware about good hygiene. But even if they do know how to practice good sleep hygiene, many teens are forced to forego it in order to cram for a test or fit in their extracurriculars.

Benefits of later school start times

Overwhelmingly, the current body of research suggests that later school start times are better for adolescents.

Generally, it follows that with later school start times, students spend that extra time sleeping, and wake up later in the mornings. As a result, they get more sleep, resulting in significant benefits to their overall well-being. Most studies have found that delaying start times by just 30 minutes can make a huge difference.

Sleep benefits to later school start times
  • Increased sleep duration
    Later rise times
    Increased daytime alertness
    Fewer instances of falling asleep in class
Other benefits
  • Better attendance (less sick days or tardies)
    Fewer drowsy driving accidents
    Fewer symptoms of depression and anxiety
    Better academic performance (improved GPA, state test scores, and college admissions test scores)
    Faster reaction times
    Fewer disciplinary actions
    Better relationships with family

Unfortunately, and perhaps surprising given the persuasive list of benefits above, many parents are actually opposed to later start times. It would impact their daily routines, and they don’t understand how critical sleep is to their child’s health and academic performance. According to a University of Michigan survey, just 51% of parents support later school start times.

" We found that parents underestimated how much sleep their children needed, and only about half agreed with existing recommendations that school start times should be later. [But] there's evidence that it's a win-win for everyone. We cannot change teens' biology to have them sleep earlier, so we should push the school start times back, in line with recommendations from the American Academy of Sleep Medicine and the American Academy of Pediatrics. "

- Galit Dunietz, PhD

School start times and sleep: study findings

Below you’ll find our review of the current literature surrounding school start times, adolescent sleep, and academic performance. Studies are organized chronologically, from most to least recent.

Later Start, Longer Sleep: Implications of Middle School Start Times, School Health 2018

Nearly 1,000 junior high students (7th and 8th graders) from 11 schools participated in this Children’s National Health System study, divided between those attending schools with average 8am start times and those with 7:23am start times. Both parents and students filled out online surveys during the study.

Key findings:

  • A start time delay of 37 minutes resulted in 17 more minutes of sleep.
  • Students who attended schools with later start times reported less daytime sleepiness, and higher levels of daytime alertness.

benefits of later school start times

" Going to sleep earlier to allow for earlier start times is not possible for many teens as their biological clocks are delayed, at least relative to younger children and adults. We know that when we do not go to bed and wake at optimal times there are increased risks for physical and mental health problems. "

- study author Daniel S. Lewin, PhD

Sustained benefits of delaying school start time on adolescent sleep and well-being, Sleep 2018

This study looked at 375 students at an all-girls’ high school in Singapore. The researchers worked with the school to delay their start times by 45 minutes, in order to evaluate the impact on the students on a short-term and long-term basis.

The researchers were also particularly interested in how the later school start time would affect students’ behaviors and societal acceptance, given the large focus on academic success in East Asian countries.

Key findings:

  • One month after the later start time was implemented, students went to bed 9 minutes later, but they woke up 31.6 minutes later, enjoying a total 23.2 more minutes of sleep.
  • Nine months later, students maintained the 9-minute delayed bedtime, but they slept for an additional 10 minutes.
  • At both the short-term and long-term check in, students reported higher levels of emotional well-being and lower levels of sleepiness.
  • Longer sleep durations were correlated with higher improvements in daytime alertness and emotional wellbeing.
  • The majority of parents (75.6%), teachers (67.6%), and students (89.1%) agreed that the later start times were better for students.

later school start times associated with lower symptoms of depression

" Starting school later in East Asia is feasible and can have sustained benefits. Our work extends the empirical evidence collected by colleagues in the West and argues strongly for disruption in practice and attitudes surrounding sleep and wellbeing in societies where these are believed to hinder rather than enhance societal advancement. "

- lead researcher, Michael Chee, MBBS

High school start times after 8:30 am are associated with later wake times and longer time in bed among teens in a national urban cohort study, Sleep Health 2017

Over 400 high school students from twenty American cities completed daily sleep diaries to provide data for this study.

Key findings:

  • Students with the earliest start times slept 46 minutes less per night on average.
  • The latest school start times correlated with more time in bed.later school start times allow for more sleep
  • Students with the earliest bedtimes did go to bed earliest, but that did not correlate to longer sleep durations.
  • The only students who received at least a minimum of 8 hours of sleep were those with 8:30am or later start times.

bedtime not affected by school start times

" The presumption is if you let kids start school later they will simply go to sleep later and still not get enough sleep. But that’s a hypothetical scenario. There wasn’t data to back that up. "

- researcher Orfeu M. Buxton, PhD

Youth sleep durations and school start times: a cross-sectional analysis of the COMPASS study, Sleep Health 2017

This large-scale study included over 35,000 high school students from 78 schools in Ontario and Alberta, Canada. Controlling for race/ethnicity, school area, median household income, and sex, the researchers analyzed whether the students’ reported sleep duration was affected by their school start times.

Key findings:

  • For every 1 hour delay in start time, students slept 7 minutes longer and were 1.17 times likelier to get sufficient sleep.

Delayed high school start times later than 8:30am and impact on graduation rates and attendance rates, Sleep Health 2017

Over 30,000 students from 29 public high schools participated in this study to determine the effect of later school start times on graduation and attendance rates. The study compared graduation and attendance rates before and after delaying the school start times.

Key findings:

  • Later school start times were correlated with an increase in both graduation and attendance rates, with a larger improvement for graduation times. In the chart below, the median line is demonstrated by a black bar, and the pre-delayed start times are on the left.

graduation rates by school start time how school start times affect attendance rates

A process-oriented model linking adolescents’ sleep hygiene and psychological functioning: the moderating role of school start times, Sleep Health 2017

Researchers collected data from nearly 200 students nationwide between the ages of 14 and 17. Students completed surveys about their basic sleep hygiene, circadian chronotype (“night owl” or “early bird”), and school start times. Students were then separated into two groups, based on whether they started before or after 8:30 am (as recommended by the AAP). Students kept a sleep diary for 7 days, marking their sleep hygiene behaviors, assessing their sleep quality and duration, and whether they experienced any symptoms of depression or anxiety.

Key findings:

  • Overall, good sleep hygiene was associated with fewer symptoms of depression or anxiety.
  • Students with later school start times had even fewer depression or anxiety symptoms.
  • Students with earlier start times experienced more depression and anxiety, whether or not they practiced good sleep hygiene. This suggests that good sleep hygiene could be a moderating factor, and when combined with later school start times, can improve better sleep and quality of life for teens.
" [O]urs is the first to really look at how school start times affect sleep quality, even when a teen is doing everything else right to get a good night’s sleep. While there are other variables that need to be explored, our findings show that earlier school start times seem to put more pressure on the sleep process and increase mental health symptoms, while later school start times appear to be a strong protective factor for teens. "

- lead researcher Jack Peltz, PhD

Later school start times in the U.S., RAND Corporation 2017

A large reason why schools have not suddenly changed their start times in response to all this research is an obvious one: cost. It costs money to make sweeping changes like these, with a large part of that cost coming from the changes to bus schedules. Currently bus schedules are staggered by high school and elementary start times, so more busses and drivers would need to be employed in order to transport all students at the same time.

This study was unique because as opposed to looking at the sleep health impacts of school start times, RAND analyzed the economic impacts. Study authors used benefit-cost projections of 47 states to see the effects on the U.S. economy and public health. The authors concluded that delaying school start times to 8:30 am would not only improve public health, but also the economy, and do both in a cost-effective manner.

Key findings:

  • RAND estimated a cost of $150 per student per year to change the times, and a flat cost of $110,000 to adjust per school.
  • Within 2 years, the costs of changing schools start times would already be covered by the benefits. RAND estimated an economic gain of $8.6 billion to the national economy.
  • Within 10 years, delaying school start times would result in a $83 billion gain, and $140 billion by the 15 year mark.
  • The eventual $9.3 billion yearly gain would be on par with Major League Baseball’s revenue.
  • These economic benefits stem from improved academic performance and fewer drowsy driving accidents.

economic benefits to delayed school start times

School start time and sleep in Canadian adolescents, Sleep 2016

Researchers collected school start times from 362 schools across Canada, and data from nearly 30,000 students aged 10-18. The average start time was 8:43 am.

Key findings:

  • On average, students slept just over 8.5 hours on weekdays, but 60% still reported feeling tired in the morning.
  • For every 10 minute delay in start time, the students enjoyed 3.2 more minutes of sleep, were 1.6% more likely to get enough sleep overall, and were 2.1% less likely to feel tired in the morning.
  • The students who attended schools with later start times were more likely to sleep longer, enjoy sufficient sleep, and not report feeling tired.

Examining the Impact of Later High School Start Times on the Health and Academic Performance of High School Students, University of Minnesota 2014

Researchers followed over 9,000 high school students from 8 public schools to compare academic performance and health outcomes for students at schools with earlier vs. later start times.

Key findings:

  • Schools with later start times enabled 60% more students to get at least 8 hours of sleep per night.
  • When start times were delayed to 8:35 am or later, student’s academic performance improved significantly. Their grades were higher in core subjects, they got higher scores on state and national tests, and their attendance rates improved while tardies decreased.
  • Students who slept fewer than 8 hours of sleep nightly reported significantly higher levels of depression symptoms, caffeine consumption, and substance use.
  • When a school changed start times from 7:35 to 8:55am, teenage car crashes decreased by 70%.
" Another issue is that kids who are sleep deprived tend to be snackers and more sedentary. Sleep is tied to healthy eating and exercise. "

- lead researcher Kyla L. Wahlstrom, PhD

Adolescent Sleep, School Start Times, and Teen Motor Vehicle Crashes, Clinical Sleep Medicine 2008

A study of nearly 10,000 students from a single school district analyzed the effect of a 1-hour delayed start time on student sleep duration and car accidents. Start times were delayed from 7:30am and 8:00am for high school and middle schools, respectively, to 8:30am and 9:00am.

Key findings:

  • Students’ total sleep time on weeknights increased between 12 to 30 minutes, depending on their grade.
  • The number of students getting 8 hours or more of sleep on school nights increased from 35.7% to 50%, as did the number of students getting 9 hours or more (from 6.3% to 10.8%).
  • Accordingly, the sleep debt catch up on weekends decreased from 1.9 to 1.1 hours.
  • Car crash rates fell 16.5%.

hours of sleep by grade level drowsy driving accident rate reduced after delayed school start times

Middle School Start Times: The Importance of a Good Night’s Sleep for Young Adolescents, Behavioral Sleep Medicine 2007

Over 200 middle school students participated in this study, who all attended urban public schools that started at 7:15am or 8:37am. To avoid other variables interfering with the results, the students selected for the study shared similar bedtimes, sleep hygiene practices, and weekend sleep schedules.

Key findings:

  • Students who attended schools with later start times woke up 1 hour later on weekdays and enjoyed 50 more minutes of sleep each night.
  • Students who attended schools with later start times also reported less sleepiness and fewer tardies.

Adolescent Sleep Patterns, Circadian Timing, and Sleepiness at a Transition to Early School Days, Sleep 1998

A small sample of about 30 student participants were evaluated as they transitioned from 9th grade in junior high to 10th grade at high school. They went from a school that started at 8:25 to one at 7:20am. Students kept sleep diaries, while researchers recorded additional data through actigraphy, lab evaluations, and multiple sleep latency tests (MSLT).

As one of the initial studies on adolescent sleep and school start times, this study was important in charting the change a new school start time had on sleep patterns – in isolation of other changes.

Key findings:

  • Students did not go to sleep any earlier, even though they had to wake up earlier. Bedtimes remained consistent at 10:40pm.
  • Their overall sleep duration fell about 20 minutes, from 7 hours and 9 minutes to 6 hours and 50 minutes (both of which are well below the recommended 9 hours).
  • Students scored poorly on MSLT, displaying a pattern similar to narcolepsy.
" Even without the pressure of biological changes, if we combine an early school starting time--say 7:30 am, which, with a modest commute, makes 6:15 am a viable rising time--with our knowledge that optimal sleep need is 9 1/4 hours, we are asking that 16-year olds go to bed at 9 pm. Rare is a teenager that will keep such a schedule. School work, sports practices, clubs, volunteer work, and paid employment take precedence. When biological changes are factored in, the ability even to have merely 'adequate' sleep is lost. "

- lead researcher Mary A. Carskadon, PhD

Additional resources

Educational materials

  • Tuck’s Parent’s Guide to Healthy Sleep covers the unique sleep needs and challenges that present at every age, from infancy to adolescence. Parents can learn about healthy sleep recommendations for their children and read tips for helping them get it.
  • Sleep Deprivation in Adolescents and Young Adults is a short paper by the National Adolescent and Young Adult Health Information Center outlining the sleep needs of adolescents and what’s keeping them from getting sleep, with sleep tips and links  to additional resources.
  • Later School Start Times Promote Adolescent Well-Being is an educational brochure by the American Psychological Association providing an overview of the benefits teens experience from delayed school start times.

Studies and research groups

  • Causes and consequences of sleepiness among college students is a 2014 review of college-age young adults and their sleep patterns. While start times differ depending on classes, many of the sleep hygiene practices students develop in high school continue into college, where they continue to live in a state of sleep deprivation.
  • The Adolescent Sleep, Health, and School Start Times national conference is held annually, connecting researchers, educators, legislators, and more. Sessions are research-based and advocate for later school start times.
  • The University of Minnesota has a dedicated research program and conference dedicated to delaying school start times. They publish their latest study findings on the website.
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