Gov. Gavin Newsom called on Tuesday for a statewide ban on smartphone use in California schools, joining a growing national effort to curb cyberbullying and classroom distraction by limiting access to the devices.

Mr. Newsom, who has four school-age children, said he would work this summer with state lawmakers to dramatically restrict phone use during the school day in the nation’s most populous state. His directive came hours before board members at the Los Angeles Unified School District, the country’s second-largest school district, voted to pursue their own smartphone ban that could begin in January.

“When children and teens are in school, they should be focused on their studies, not their screens,” Mr. Newsom said in a statement.

The effort to curb devices on campus has transcended political lines, as Republican-led states like Florida and Indiana already have instituted their own restrictions. New York City leaves it up to individual campuses to determine their own policies after dropping a blanket cellphone ban in 2015, but Gov. Kathy Hochul said last month that she would pursue a statewide prohibition in 2025.

The moves in California followed a call this week for warning labels on social media platforms by the U.S. surgeon general, Dr. Vivek Murthy, who argued that they were fueling a mental health crisis among adolescents.

“Adolescents who spend more than three hours a day on social media face double the risk of anxiety and depression symptoms,” Dr. Murthy wrote on Monday in an opinion piece for The New York Times. “And the average daily use in this age group, as of the summer of 2023, was 4.8 hours.”