Later School Start Times Show Positive Impact On CA Test Scores And Mental Health, Study Finds

SACRAMENTO, CA — A new study from the National Bureau of Economic Research indicates California's middle and high school students have benefited from later start times mandated by Senate Bill 328.

Among the most positive effects since the law went into effect in the 2023-23 school year, the study found more students are sleeping at least eight hours a night — an increase of 13%, with boys and Hispanic students showing the largest gains with sleep.

Eight hours of sleep per night is the CDC-recommended minimum for the age group of students in middle and high school, the study said.

Boys in particular showed "statistically significant" declines in sadness, hopelessness, and suicidal ideation, according to the study.

The study, released in May, focused on California Senate Bill 328, which was signed into law by Gov. Gavin Newsom in 2019, and went into effect on July 1, 2022. The bill requires classes at most public schools, including middle and high schools, begin no earlier than 8 a.m., and 8:30 a.m., respectively.

The working paper titled "Breaking the Early Bell: Lessons from the First Statewide Mandate on School Start Times" also noted students reported improved mental health and better test scores in English, math and science.

Math and English scores for 8th graders improved by approximately "0.08-0.10 standard deviations, with the largest gains among Hispanic and economically disadvantaged students."

"A within-state analysis using teachers' commute arrival times as a proxy for pre-policy school start times corroborates these findings, and shows academic gains accumulating over 2023-2025 alongside a suggestive decline in high school dropout rates," the study said.