The requirement cements the standing of the L.A. Unified School District as an early adopter of COVID-19 school safety measures that are wide-reaching and aggressive. The nation’s second-largest school system has moved faster and more comprehensively than most others in testing all students and employees for coronavirus infection every week, requiring masks indoors and outdoors and ordering employees to get vaccinated.

L.A. schools Interim Supt. Megan K. Reilly said the student mandate was the next logical step to keep children, staff and community members safer from a COVID-19 pandemic that still poses significant risks.

“We’ve always approached safety with a multilayered approach: masks, air filtration and coronavirus screening,” Reilly told The Times. “But we are seeing without a doubt that the vaccines are one of the clearest pathways to protecting individuals from getting severe sickness as well as for mitigating transmission of the COVID virus. It is one of the best preventive measures that we have at our disposal to create a safe environment at schools.”

New York City’s school system, the largest in the nation, so far has ordered athletes in high-contact sports to begin the vaccination process before competition starts. New York City and Chicago, the nation’s third-largest district, are among a growing number of school systems that have enacted mandates for employees.

The L.A. district action “could provide the model for a comprehensive school response to COVID mitigation, so that schools can move on to student academic and mental health recovery plans,” said Odis Johnson Jr., executive director of the Center for Safe and Healthy Schools at the Johns Hopkins University School of Education. “Mandatory vaccination mandates move us forward toward finally addressing students’ developmental, social and academic well-being.”

One vaccine, made by Pfizer, has received full approval by the U.S. Food and Drug Administration for people 16 and older. Those who are 12 to 15 can be inoculated under a federal emergency use authorization. L.A. Unified is not waiting for full vaccine approval for those 12 to 15 — although that approval by the FDA is widely expected in the coming weeks. And President Biden on Thursday pledged to expedite approval of the vaccine for younger children.

Reilly estimated that about 225,000 students in grades six through 12 would fall under the policy. District officials estimate that roughly 80,000 students are not yet vaccinated. Also affected would be about 17,000 students in independent charter schools that use L.A. Unified campuses.

Students who are not vaccinated by the deadline will not be allowed on campus, she said. The alternative for them would be to enter remote learning through independent study, a program that was overwhelmed at the start of the school year when more than 10,000 students signed up.

Under the district’s mandate, the first students affected would be those involved in any school-sponsored extracurricular activity, including sports, drama, chorus and band. Those students who are 12 or older must receive a first vaccine dose no later than Oct. 3 and a second dose no later than Oct. 31.

All students 12 and older would have to receive a first dose no later than Nov. 21 and a second dose no later than Dec. 19. The final day of classes before winter break is Dec. 17.

Students return to class on Jan. 11. By Jan 10, proof of vaccination would have to be “uploaded and approved in LAUSD’s Daily Pass program” except for those students with approved exemptions,” the proposal says.