California’s mandate requiring later start times for middle and high schools is yielding results, with students sleeping more, reporting better mental health and scoring higher math and English scores, according to a new study.
The new working paper from the National Bureau of Economic Research said Senate Bill 328, which went into effect in 2022, requires most middle schools to start no earlier than 8 a.m. and high schools no earlier than 8:30 a.m.
The study found that the new law increased the share of students sleeping at least eight hours per night by 13%, meeting the minimum recommended for adolescents by health experts. The largest jump was among boys.
The study shows that “rest and sleep are incredibly important in the function of schools,” said Osea Giuntella, an author of the report. Although the short-term increase in sleep is moderate, it has led to significant improvements in mental health and academic outcomes, he said.
Giuntella, a University of Pittsburgh researcher who studies sleep and economics, said the study’s first-year results are consistent with previous research linking better sleep to improved student well-being and academic performance. The study used changes in teachers’ commute arrival times from the American Community Survey as a proxy for later school start times, comparing sleep and mental health data before and after the law took effect in the 2022-2023 school year and tracking academic gains from 2022 through 2025.
Gains in sleep, mental health, English and math
Students reported experiencing better mental health since schools shifted to later start times, with boys reporting the largest reductions in sadness, hopelessness and suicidal ideation, and Latino students reporting the biggest drop in difficulties concentrating.
Terra Ziporyn, executive director at nonprofit Start Schools Later and longtime advocate of later school start times, said the measure was a key part of California’s response to what schools have described as a student mental health crisis.
“The first step in addressing student mental health problems is to not create them in the first place,” Ziporyn said. “You can get a lot of counselors, but systematically depriving an entire adolescent population of adequate sleep is a surefire way to hurt their mental health.”
The study also found significant improvements in academic achievement, with eighth-grade students making measurable gains in math and English, particularly among Hispanic and economically disadvantaged students.
Giuntella said the improvement in scores was probably “largely driven by the change in sleep” based on comparable studies where increased sleep led to higher grade-point averages. That’s also why Latino students, who are already less likely to get adequate sleep than white students due to lower family income and family and work responsibilities, improved their math and English scores the most, he said.
Some parents have said later start times complicate work commutes, push back sports and extracurricular activities, and lead to some students simply pushing back the time they go to bed.
The study found that sports and extracurricular activities did start later after the change to later start times, but the changes were “marginal and not statistically significant,” Giuntella said.
California can improve its implementation of SB 328 by collecting statewide data on later school start times to “assess the impact of the reform.” In the meantime, schools can take from the study that later start times are “effective and powerful tools” for student outcomes, Giuntella said.
Sanganeria is a reporter for EdSource, a nonprofit, nonpartisan journalism organization covering education in California.
