California Gov. Gavin Newsom signed a law Monday mandating schools to limit or ban smartphone use, in response to growing concerns that excessive screen time may heighten the risk of mental illness and hinder learning.

As many as 13 other states this year have banned or restricted cellphones in school or recommended local educators do so, after Florida led the way by banning phones in class in 2023, according to Education Week.

California, with nearly 5.9 million public school students, has followed the lead of its own Los Angeles County, whose school board banned smartphones for its 429,000 students in June.

That same month U.S. Surgeon General Vivek Murthy called for a warning label on social media platforms, akin to those on cigarette packages, likening the problem to a mental health emergency.

Murthy cited a study in the medical journal JAMA showing adolescents who spend more than three hours a day on social media may be at heightened risk of mental illness, while referring to a Gallup poll showing the average teen spends 4.8 hours per day on social media.

California's bill, which passed 76-0 in the state assembly and 38-1 in the senate, requires school boards or other governing bodies to develop a policy to limit or prohibit student use of smartphones on campus by July 1, 2026, and update the policy every five years.

"We know that excessive smartphone use increases anxiety, depression, and other mental health issues – but we have the power to intervene. This new law will help students focus on academics, social development, and the world in front of them, not their screens, when they're in school," Newsom said in a statement.