THE SCIENCE is clear. Adolescents are physiologically and neurologically wired to sleep later, and the research showing the health and educational benefits of later school start times for teens is compelling. So credit to California for addressing this significant public health issue by insisting that public schools set schedules that allow youths to get the sleep they need to learn and thrive.

Gov. Gavin Newsom (D) has signed into law legislation that mandates later start times at most public middle and high schools. Under the law, to be phased in over three years, classes for high schools will start no earlier than 8:30 a.m. and classes for middle schools will start no earlier than 8 a.m. Optional before-school periods are allowed, and rural districts are exempt due to travel and distance circumstances. But it is estimated that between 80 percent and 90 percent of the state’s 3 million public middle and high school students will benefit.

An increasing number of school districts across the country have implemented later school start times for adolescents, but California is the first state to order the shift as a matter of law. Opponents had argued that the question of when to start school should be left up to local decision-makers and similar legislation was vetoed in 2018 by former governor Jerry Brown (D). Mr. Newsom was right in recognizing the state shouldn’t shirk its responsibility to do what is best for students and that the public will benefit from the improvements in student health, safety and academic performance.

The bill, based on recommendations from the American Academy of Pediatrics, was backed by leading public health and medical experts. “The volume, breadth, consistency and strength of the peer-reviewed scientific research supporting this legislation are unequivocal, and they exceed the high standards for public health and education policy,” more than 120 experts wrote in support of the measure to Mr. Newsom.

No doubt there may be some challenges in figuring out the logistics of later school times. But the success of school districts that have undertaken this change show that it is not only possible but also well worth the effort in terms of better outcomes for students.

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