• Calif. first state to require vaccines or weekly tests for all teachers, school staff,

SAN FRANCISCO — California will become the first state in the nation to require all teachers and school staff to get vaccinated or undergo weekly COVID-19 testing, as schools return from summer break amid growing concerns about the highly contagious delta variant, Gov. Gavin Newsom announced Wednesday.

The new policy applies to both public and private schools and will affect the state’s 320,000 public school teachers, more than 250,000 support staff — from cafeteria employees to cleaners — and at least 80,000 private school employees, according to the California Department of Education and labor unions. It will also apply to school volunteers.

Mr. Newsom announced the new policy at a San Francisco Bay Area school that reopened earlier this week to in-person classes. Many California schools are back in session, with others starting in the coming weeks.

“We think this is the right thing to do, and we think this is a sustainable way to keeping our schools open and to address the number one anxiety that parents like myself have for young children,” said Mr. Newsom, who is a father of four. “That is knowing that the schools are doing everything in their power to keep our kids safe.”

Several large school districts in the state have issued similar requirements in recent days, including San Francisco, Oakland, San Jose and Long Beach Unified.

California, like the rest of the country, has seen a troubling surge in COVID-19 infections because of the delta variant, which represents the vast majority of new cases. It has affected children more than previous strains of the virus, prompting a growing number of teachers unions to ease earlier opposition to vaccine mandates.

California’s two largest teachers unions, both powerful political allies to the governor, said Wednesday they fully supported Mr. Newsom’s policy.

The California Teachers Association and the California Federation of Teachers both cited state and national polling that indicates nearly 90% of educators have been vaccinated but said the rising spread of the delta variant, particularly among children, makes the new policy necessary. Children under 12 are not yet eligible to be vaccinated.

Over the past few weeks, Mr. Newsom has mandated that all health care workers must be fully vaccinated and required that all state employees get vaccinated or choose weekly testing.

Vaccine mandates are perilous for the Democratic governor, who faces a recall election next month fueled in part by anger over his handling of the pandemic.

California was the first state to order a pandemic lockdown in March 2020, which shuttered businesses and schools statewide. While many private schools maintained in-person classes, most public schools kept students in distance learning for up to a year. Many public schools finally reopened last spring, lagging much of the country.

Details of how the new policy will be enforced were not announced. Labor unions say those logistics still need to be worked out.

Schools are required to be in full compliance with the new policy by Oct. 15, giving schools time to verify vaccination status and have in place weekly testing for unvaccinated staff, said Amelia Matier, a spokeswoman in the governor’s office.

Mr. Newsom did not rule out expanding the requirement to students after a vaccine is approved for children under 12 years old.