As an adult, I don’t have much trouble adjusting my sleep schedule when I need to wake up early. I just go to bed earlier the night before.
Teenagers, however, don’t seem to work that way. Adolescent sleep patterns are biologically different, making it difficult for them to compensate for early wake-up times. As a result, one of the most effective policies for improving student outcomes in middle and high school is delaying school start times. A recent NBER study provides the latest evidence. The authors examine a California law requiring middle schools to start no earlier than 8:00 a.m. and high schools no earlier than 8:30 a.m. Most schools were affected. After the policy was implemented, total sleep duration increased by an average of about 40 minutes, and the share of students sleeping at least eight hours per night increased by 13 percent.
The effects on academic achievement were substantial. Math and English test scores increased by 0.08 to 0.10 standard deviations—roughly the difference between having a highly effective teacher rather than an average one. These gains are larger than what we would expect from any feasible class-size reduction in middle or high schools.
The study also examined mental health outcomes. While those estimates are less precise, the results suggest improvements in mental health, particularly for boys.
This new NBER study is not an outlier. It adds to a large body of well-identified research reaching the same conclusion: when schools start later, teenagers get more sleep and perform better.
The policy implications are straightforward, though implementation is not always easy. One concern is that parents cannot always shift their work schedules, especially when younger children need supervision before school. But for families facing this challenge, before-school programs can help fill the gap.
Another concern is transportation. Many districts stagger start times so buses can serve multiple schools, meaning some students must start early. Yet this is ultimately a scheduling problem. Districts could shift the entire school day later, allowing students to start and finish later while still leaving plenty of time for after-school activities and family dinners.
The evidence is clear that teenagers benefit greatly from delaying school start times. Missouri school districts should carefully weigh the trade-offs and consider practical adjustments to give our kids more time to sleep.
