California school start time mandate improves student sleep and mental health

A new working paper from the National Bureau of Economic Research indicates that California’s mandate for later school start times is producing positive outcomes for students. The study examines the effects of Senate Bill 328, a 2022 law requiring most middle schools to start no earlier than 8 a.m. and high schools no earlier than 8:30 a.m.

Findings show a 13% increase in the number of students getting at least eight hours of sleep per night, with the most significant increase observed among boys. Beyond sleep, the study reports improvements in mental health and academic performance in math and English. Specifically, boys reported reductions in sadness, hopelessness, and suicidal ideation, while Hispanic students showed improved concentration.

Osea Giuntella, a researcher from the University of Pittsburgh and author of the report, noted that while the increase in sleep is moderate, it has led to significant improvements in student well-being and academic results. The study utilized teacher commute data as a proxy for start time changes to track these developments from the 2022-2023 school year through 2025.