In order to resume in-person class instruction, a county must have been off the state's COVID-19 watch list for 14 consecutive days. Districts in counties on the watch list will only be able to do distance learning.
As of Friday, 33 of California's 58 counties are on the COVID-19 watch list, including Los Angeles, Orange, Riverside and San Bernardino counties. That represents more than 80% of the state's population.
Until now, decisions on how and when to reopen have largely been left up to individual school districts.
The state's former guidelines for reopening schools recommended mask wearing for students, but now face coverings will be required for students in third grade and higher. Face coverings are recommended but not required for kindergarteners, first graders and second graders.
Masks will be required for all teachers and staff, who will also be required to get tested for the virus regularly.
The governor also announced new rules on when schools will be forced to close back down:
Despite challenges, LAUSD parents say distance learning is best for upcoming school year
"Schools must provide meaningful instruction during this pandemic whether they're physically open or not," Newsom said. "We all prefer in-classroom instruction for all the obvious reasons, but only if it can be done safely."
Even for schools that only do online distance learning, Newsom said the state will be making sure there are "rigorous" standards.
"If we're going to have distance learning, we will make sure that it's real, that we address the divide and it is quality," the governor said. "Learning is non-negotiable."
Newsom said the new guidelines apply to K-12 education in the state. He added he is working with California's universities to agree on health and safety guidelines that should be released in the coming weeks.
California reported 9,986 new coronavirus cases over the past 24 hours. As of Friday, COVID-19 patients occupy about 16% of the state's ICU capacity.
With many California school districts just three or four weeks away from fall instruction, many are opting for full-time online distance learning amid the coronavirus pandemic. That's the smart move for much of the state, said State Superintendent of Public Instruction Tony Thurmond in a virtual press conference Wednesday.
"I think that if school opened tomorrow, most of our districts would open in distance learning," said Thurmond. "And that is a decision that I think is a good decision if conditions don't change right now."
Thurmond called for "an abundance of caution" as many of California's 1,000 school districts finalize plans for the new school term.
"In any place where there is uncertainty, we should proceed with caution. In many cases, that's going to be opening in distance learning," Thurmond said in a weekly media briefing held online.
However, there is no one-size-fits-all template for reopening schools, and classroom learning can still happen in counties or districts where it can be done safely, he said.
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Last month, the California Department of Education released 62 pages of guidelines for districts on how to safely reopen. The guide laid out recommendations for taking temperature upon entering buses and schools, spacing out desks, cutting class sizes and rigorous cleaning of campuses and hand sanitizing for students and staff. But that was before California's case count exploded.
"Since we've issued our guidance, conditions have changed dramatically," said Thurmond. "We know that in many communities throughout our state we're seeing high rates of infection in the community."
The Los Angeles and San Diego school districts, the two largest in California with a combined K-12 student population of about 720,000, announced Monday their school years will begin next month with distance learning because of rising coronavirus hospitalizations and infection rates.
"We applaud the superintendents and school boards in Los Angeles and San Diego for making the decision to say, 'Lets open 'safely,' " Thurmond said.
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L.A. and San Diego are the latest in a growing number of California school districts choosing to start the new term with digital learning amid strong concerns from teachers unions about the safety of staff on school campuses.
Oakland, Long Beach and San Bernardino districts are among those that already have have said they will start off with distance learning. Some districts are considering a mix of distance learning and classroom instruction with few students in the room.
Meanwhile, the superintendent of the El Segundo Unified School District posted a letter to parents online on Wednesday, stating that hybrid learning and distance learning will be offered for the upcoming school year, but that decision is contingent on Newsom's announcement.
Thurmond acknowledged the safest way forward for much of the state is to keep classrooms closed for now, and pivot to some in-person instruction if and when coronavirus conditions improve.
"We are concerned with the increase in hospitalizations, and the fact that those needing hospitalizations are needing intensive care at a higher rate," said Dr. Muntu Davis, with the Los Angeles County Department of Public Health.
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KGO-TV and the Associated Press contributed to this report.