From homework and studying to sports, clubs, and part-time jobs, students often maintain packed and constantly shifting schedules in high school. But those schedules can keep students from getting to bed at a consistent time.
New research in Sleep, the peer-reviewed journal of the Sleep Research Society, suggests irregular sleep—not just overall amount—can play a significant role in students’ academic and behavior problems in high school.
The study was part of ongoing research funded by the National Institute of Child Health and Human Development using data from the longitudinal Future of Families and Child Well-Being study, which tracks the development of 5,000 urban children from birth to age 22. In the current study, Stony Brook University researchers led by Gina Marie Mathew and Lauren Hale analyzed data from about 800 teenagers who reported their school grades and behavior and also wore wrist devices that allowed researchers to track their sleep patterns over several days.
Across the board, the teenagers were sleep deprived. On average, they got about 7.5 hours of sleep a night—somewhat normal for adults but about 1.5 hours less than the American Academy of Pediatrics recommends for adolescents.
A separate 2023 study from the federal Centers for Disease Control and Prevention found students who get at least eight hours of sleep a night have better mental health and academic achievement. But prior studies find teenagers’ sleep habits have grown less consistent and late-night screen time has risen in the last decade.
While adults (including teachers and principals) can also suffer from irregular sleep, high schoolers are particularly vulnerable, Mathew said, because sleep cycles naturally change during adolescence.
“Instead of wanting to go to bed at nine, you could want to sleep but only at 11:00 p.m. or maybe even 12:00 a.m.,” she said. “But then, especially if you have an early school start time, you’ll get short sleep during the school week and then on the weekend try to make it up by sleeping in later. And so this shifting of bedtimes and wake times across the week increases sleep variability.”
However, researchers found students’ sleep schedules were much more closely linked to their academic progress and behavior than the overall amount they slept. In particular, students who more frequently went to bed later or varied the number of hours they slept, earned an A in fewer classes by the end of the year. Students with more irregular sleep were also more likely to earn a D or worse in multiple classes by the end of the year.
Students who slept inconsistent hours were also more likely to report getting in trouble at school and were more likely to have been suspended or expelled in the last two years.
“Sleep variability is really coming up now as being so important for so many aspects of health and well-being—mental health, for example, and cardiometabolic health,” Mathew said.
It’s not yet clear how much students’ sleep schedules can change before their learning and emotions start to suffer. Although students of color and low-income students are more likely to be sleep deprived overall, the researchers in this study did not look at whether unstable sleep patterns affect some groups of students more than others.
Still, the study may provide additional evidence in favor of later school start times, a schedule change that has been gaining traction in some districts and among educators. While the average secondary school start time in 2023 was 8:07 a.m. (and 10 percent start by 7:30 a.m.) the American Academy of Pediatrics recommends start times no earlier than 8:30 a.m. for adolescents.
“If anything, it supports the idea that we should be shifting school start times to be more aligned with [teenagers’] rhythms and how they work best,” Mathew said.
