Schools shift as evidence mounts that later start times improve teens’ learning and well-being (2024)

At a glance

• Research from psychologists and others indicates that later school times correlate with more sleep, better academic performance, and myriad mental and physical health benefits.
• Adolescents between the ages of 13 and 18 should sleep 8 to 10 hours per day, according to the American Academy of Sleep Medicine. But few are logging those hours.
• During puberty, youth undergo a shift in their circadian clocks that makes it harder for them to fall asleep until later in the night. Meanwhile, they can stay awake longer before experiencing an increase in the pressure to sleep.
• Pushing back school start times has added sleep benefits for teachers and parents, too.
• States and school districts are mandating later school start times in response to the scientific research.

Sleep is a key ingredient in physical and mental health, and most adolescents aren’t getting enough—but a straightforward solution is within reach. For decades, psychologists and other researchers have amassed evidence that later school start times can improve adolescents’ health and well-being. Emerging evidence suggests that pushing back the first bell can benefit teachers’ and parents’ sleep, too. Finally, that evidence is translating to broad shifts in policy.

In the past 25 years, more than 500 individual school districts in the United States have moved school start times later in response to the research, said Kyla Wahlstrom, PhD, an educational policy researcher at the University of Minnesota, who has been studying start times since the 1990s. But progress was piecemeal until 2014, when the American Academy of Pediatrics helped draw attention to the cause by publishing a position statement stating that middle schools and high schools should begin no earlier than 8:30 a.m. In 2019, California passed a law, enacted in 2022, mandating secondary schools start after 8:30 a.m. Florida passed a similar bill in 2023, and several other states are now considering such legislation.

Yet opposition to changing established start times can be surprisingly fierce. “There are always roadblocks. Change is hard,” said Lisa Meltzer, PhD, a pediatric sleep psychologist with Nyxeos Consulting and a professor at National Jewish Health in Denver. But the evidence is clear, she adds. “This is a systemic change that can really make a big difference for so many.”

Adolescents between the ages of 13 and 18 should sleep 8 to 10 hours per day, according to the American Academy of Sleep Medicine. Few are logging those hours. Between 2009 and 2021, the percentage of high school students who did not get enough sleep increased from 69% to 77%, according to data from the CDC National Youth Risk Behavior Surveys. In 2021, nearly 70% of 9^th graders, and 83.5% of 12^th graders, failed to get enough sleep.

Many factors are at play in youth getting too little sleep, including heavy homework loads, overscheduled extracurriculars, and the irresistible lure of social media, which has been shown to impact adolescent sleep (van den Eijnden, R. J. J. M., et al., International Journal of Environmental Research and Public Health, Vol. 18, No. 3, 2021). Yet the biggest factors are biological. During puberty, youth undergo a shift in their circadian clocks. That shift makes it hard for teens to fall asleep until later in the night. Another factor at play is the sleep homeostatic system, which controls the rhythm of sleepiness and wakefulness. The longer you stay awake, the greater the pressure to sleep becomes. There’s evidence that during adolescence, that pressure takes longer to build. Those biological influences famously drive teens to sleep later in the morning. But even sleeping until noon on weekends isn’t enough to make up for the sleep deficit they accumulate night after night during the school week.

Neurological and psychological diagnoses only compound the problem. Sleep problems, including difficulties falling or staying asleep, are common in kids with autism and ADHD. Anxiety and depression can also skew sleep patterns. As rates of these conditions have increased, so has the number of kids coming to school bleary-eyed each morning. Pushing back start times has a direct impact on how much kids sleep. It’s no surprise that teens wake up later when their school day starts later. Notably, though, they tend to go to bed around the same time—resulting in more time under the covers, as Meltzer, Wahlstrom, and colleagues showed in a longitudinal study (Sleep, Vol. 44, No. 7, 2021).

The downstream benefits are significant. One meta-analysis found that compared with students whose schools started between 8 a.m. and 8:29 a.m., those in schools starting between 8:30 a.m. and 8:59 a.m. had longer sleep duration, less negative mood, and better developmental outcomes including socioemotional health, cognitive development, behavioral health, and physical health (Pediatrics, Vol. 149, No. 6, 2022). Another review found later start times were correlated with better attendance, less tardiness, less falling asleep in class, better grades, and fewer car crashes (Wheaton, A. G., et al., Journal of School Health, Vol. 86, No. 5, 2016).

“Adolescent health is significantly improved by having later start times,” Wahlstrom said, with reductions in substance use, suicidality, and depression. “This isn’t a silver bullet to improve test scores. It’s a public health policy.”

Students aren’t the only ones to benefit from sleeping in. Meltzer and Wahlstrom found that after new school start times were implemented in a large suburban district near Denver, more parents of middle and high school students reported sufficient sleep duration, and fewer reported feeling tired (Sleep Health, Vol. 8, No. 1, 2022). For their part, middle and high school teachers reported later wake times, increased sleep duration, and improved daytime functioning (Journal of School Health, Vol. 93, No. 2, 2022). “The high school teachers said this profoundly changed their lives, allowing them to be a more effective teacher,” Wahlstrom said.

It’s an important finding, given that many educators report feeling overstressed and under-rested, said Michelle Perfect, PhD, a professor of school psychology at the University of Arizona and past president of APA Division 16 (School Psychology). Her research has found that inadequate sleep duration and poor sleep quality are common among teachers. In a study not yet published, she tested teachers’ performance on a decision-making task in the lab. On the first task, teachers with poor sleep performed similarly to those who were better rested. But with each subsequent trial, their skills slipped. “By the fifth trial, they were only a few points away [on average] from a score consistent with early-stage dementia,” she said. “Teachers are making decisions constantly as they manage their classrooms. You can imagine the teacher in a classroom for 8 hours getting more and more fatigued by doing simple tasks.”

Despite the evidence that later start times have broad benefits, making the change can be complicated. To accommodate later starts for teenagers, most districts need to shift elementary start times earlier to balance busing schedules—a move that often gets pushback from families. In general, though, it’s easier for young kids to get used to going to bed and waking up earlier, since they don’t have the biological pressures of puberty fueling their sleep drive. Moreover, while teens benefit from later start times, elementary students don’t seem to suffer negative effects from earlier schedules, Meltzer said. “Their bedtimes are more adjustable.”

Families also have concerns about how new start times might impact after-school schedules. Districts may need to get creative, adjusting sports timetables when playing districts on different schedules and rearranging the child-care offerings available before and after school. But districts that have made the switch have risen to those challenges, Meltzer said, and her research shows that later start times haven’t been found to significantly interfere with teens participating in extracurricular activities or holding after-school jobs (Frontiers in Sleep, Vol. 1, No. 1044457, 2022).

School start times alone won’t solve the problem of too many young people getting too little sleep. “We need to pay attention to both ends of the sleep cycle—what’s happening in the morning, but after school as well,” said Mary Carskadon, PhD, a professor of psychiatry and human behavior who studies circadian rhythms at Brown University. That can mean limiting sports and other activities in the evening, avoiding phone use at night, and making sure kids aren’t sacrificing sleep for homework.

Until society does a better job prioritizing sleep, Carskadon said, kids will continue to be under-rested. But in the meantime, changing school start times will be the single biggest way to help the greatest number of adolescents get the rest they need to thrive, Meltzer added. And research findings will continue to help school boards and governments get on board with the change. With more than 27,000 public and private secondary schools in the United States, those efforts will take time. But the impact of later school start times is evident, and youth deserve the chance for better health, Meltzer said. “There are problems that have to be solved, but they’re solvable. It can be done.”

• Start School Later
• Pediatric sleep: Current knowledge, gaps, and opportunities for the future
  Reynolds, A. M., et al., Sleep 2023
• FastStats: Sleep in High School Students
  U.S. Centers for Disease Control and Prevention, 2024