Los Angeles, San Diego schools choose to go online-only in fall.

SACRAMENTO, Calif. — California’s two largest public school districts said Monday that instruction would be online-only in the fall, in the latest sign that school administrators are increasingly unwilling to risk crowding students back into classrooms until the coronavirus is fully under control.

The school districts in Los Angeles and San Diego, which together enroll some 825,000 students, are the largest in the country to abandon plans for even a partial physical return to classrooms when they reopen in August.

The decision came as Gov. Gavin Newsom announced some of the most sweeping rollbacks yet of California’s plans to reopen. Indoor operations for restaurants, bars, wineries, movie theaters and zoos were shut down statewide Monday, and churches, gyms, hair salons, malls and other businesses were shuttered for four-fifths of the population.

“There’s a public health imperative to keep schools from becoming a petri dish,” said Austin Beutner, the Los Angeles school district’s superintendent.

The California decisions are the latest blow to President Donald Trump’s push to fully reopen schools across the country this fall in order to get the economy moving by enabling parents to return to workplaces. Districts, parents and teachers have struggled to maintain the education of tens of millions of K-12 students while keeping them and their teachers healthy and safe.

At the White House, Trump denounced the decision in Los Angeles, arguing that schools should resume because children wanted to attend.

“Schools should be opened,” Trump said. “You’re losing a lot of lives by keeping things closed.” It was not clear what he meant because public health experts say the virus spreads quickly in poorly ventilated, closed areas, the condition of many U.S. schools.

Across the country, school districts are taking a patchwork approach to reopening.

New York City, the nation’s largest school district, announced last week that it would provide several days per week of in-person learning, with students working online from home the rest of the time. Seattle has also announced a hybrid model that is emerging as popular nationwide, among both large and small districts. Chicago, the nation’s third-biggest system, has not yet announced its reopening plan.

But in cities where the virus has continued to rage, efforts at compromise solutions have increasingly proven unworkable — a shattering realization for families that have strained for months to cobble normalcy out of a situation that is pitting their children’s development and education against parental livelihoods and household health.

Mahogany Taylor, a 39-yearold mother of two and the president of the San Diego Unified Council of PTAs, said the loss of in-person instruction was particularly destructive for elementary school students — many of whom cannot type — and for low-income students, who often lack internet access and who make up nearly 60 percent of San Diego Unified’s students.

At the same time, Taylor said, a districtwide survey showed that 40 percent of parents already were planning to insist on remote instruction. “We obviously believe that school is the best place for kids,” she said, “but we also want them to be safe.”

All across the nation, school officials are trying to balance safety against learning losses. Initial research showed that during the first round of school closures, American children were set back, on average, by seven months in their reading and math learning, with children from low-income families and students of color experiencing even bigger losses.

Still, district leaders in Los Angeles and San Diego said, California was not in a position to reopen schools.

“Those countries that have managed to safely reopen schools have done so with declining infection rates and on-demand testing available,” the statement said. “California has neither. The skyrocketing infection rates of the past few weeks make it clear the pandemic is not under control.”

Beutner, whose district is the nation’s second largest, said in an interview that schools “can’t just tap our heels together” like Dorothy in The Wizard of Oz and “pretend it’s appropriate to bring people back” despite “skyrocketing” rates of new infections.