The Los Angeles school district has ordered coronavirus tests for all students and staff before they return from winter break next week as a new period of high anxiety takes hold among parents and educators amid the explosive surge of the Omicron variant.

Many parents expressed fears over the rapidly spreading contagion; others are terrified about possible campus closures that could derail a return to normalcy needed for the mental health and academic recovery of their children.

Although none of the 80 school districts in L.A. County has announced a return to online learning — with 50 school systems beginning on Monday — county Public Health Director Barbara Ferrer told school leaders to brace for the worse surge yet, with perhaps 10% of students and staff testing positive at the start of school, according to those who were familiar with a morning briefing.

Senior school officials expressed worries about having enough healthy staff to stay open and securing vast numbers of rapid-result coronavirus tests. They also expressed concerns about quickly evolving rules about who must isolate and quarantine and for how long.

Worried parents are sending their children off to school, pleading with them to stay masked, wash hands and keep a distance from friends.

“Please don’t take off your mask or get into a big crowd of students,” Maria Castro told her daughter at Long Beach Polytechnic High School. “Please, my love.”

To calm her nerves, Castro went home and logged onto a Zoom session her church was offering. And with other parents, she prayed for their children.

Colleges are also grappling with many of the same issues — and most of the University of California campuses have turned to temporary remote learning and are requiring negative coronavirus tests for students to return to dorms.

At all levels, education remains far from the familiar — and stressful.

When L.A. schools Interim Supt. Megan Reilly announced the latest measures to tamp down the pandemic, she emphasized her gratitude and the need for forbearance.

“As a united Los Angeles Unified community, we will work together to ensure the safety of our students,” Reilly said in her letter to parents and staff. “We also thank our families and employees for the ongoing support and patience.”

The goal in mandating back-to-school tests, said school board member Nick Melvoin, is to provide safe, open campuses and also “peace of mind.”

The drill in the nation’s second-largest school system will mean anyone who intends to step on a campus next week to work or learn will have to show proof of a negative coronavirus test. The announcement was made hours after a hastily called special school board meeting Monday morning.

Employees not already on duty this week would receive two hours’ pay to get the testing this week. If they wait till Monday — when they are back on the clock after winter break — they will receive any time off needed to be tested but no extra pay. School employees return to work Jan. 10. The students return Jan. 11.

The baseline testing would supplement ongoing required weekly testing of all students and staff — about 500,000 swabs per week. Families may provide a PCR test or an antigen test — either from a district testing site or from elsewhere. They also may use at-home tests. But officials are asking families to have results uploaded into the district’s Daily Pass system by Sunday, Jan. 9.

The district’s plan won immediate support from unions representing clerical workers, teachers and administrators.

The decision comes as the Omicron variant of the coronavirus is spurring new infections at a record rate in Los Angeles County, estimated to be greater than at any point since the early months of the pandemic, data show. Every infected person in L.A. County is on average transmitting the virus to two other people, according to estimates from California’s COVID-19 computer models published Monday morning.

Hospitalizations and deaths have not kept pace with this rise because most county residents are vaccinated, according to local health officials, although serious complications can occur days or weeks after infection.

School districts throughout the county must follow new, tightened safety rules. All school employees across the county must use medical-grade protective masks while indoors on campus. Schools, including private schools, and school systems have two weeks to comply after reopening.

The massive L.A. school system, with the largest weekly coronavirus testing program in the nation, has 11 testing centers. Mobile testing teams are fanning out to schools, setting up temporary clinics for one day or more through Saturday.

Woodland Hills parent Pooja Shah said in an email that she’s grateful.

“I have a 4-year-old immunocompromised at home whom I worry about,” Shah said. “I am glad that baseline testing is mandatory to enter the school.”

Other parents expressed concern that Los Angeles Unified might delay the semester or revert to remote online learning.

“When the disease continues to not be severe for kids, it’s not what’s best for them,” said Robert Herron, whose child attends public school in the Mar Vista area. “And as a kicker, you penalize those with the least means to overcome academic loss, whose communities are the least able to shield themselves from the pandemic.”

Although school districts in L.A. County are not shutting down campuses, staffing shortages and high COVID rates have forced districts online in other parts of the country, including Newark, Cleveland and Atlanta, among others. In New York, student and teacher absences were reportedly high on Monday.

Alhambra Unified, in the San Gabriel Valley, welcomed its 16,000 students back to school on Monday, with new rules requiring students to mask outdoors and advising all students and staff to wear medical-grade masks while on campus. Officials hope that most will provide their own medical-grade mask.

“Currently we don’t have enough,” said public information officer Toby Gilbert. “It’s going to be a challenge, but we have met challenges bigger than this.”

The district also has begun to offer antigen testing for students and staff and is considering weekly testing for all students. Up till now, families could opt into weekly testing.

At Alhambra High School, students poured out of the gates at 3:30 p.m. Kenneth Tang, a junior who was wearing a KN95 mask, seemed unfazed by the new requirements and said he was not going to dwell on getting sick.

“The virus is not going to stop anytime soon,” he said. “You can get the virus anywhere.”

Tammy Scorcia, president of Alhambra Teachers Association, said “everybody’s nervous. … We all thought we were moving forward.”

Her school system, she said, has provided face coverings and even protective gowns, but test kits promised by the governor did not arrive in time for the resumption of classes.

State public health officials said Monday that only about half of the 6 million test kits promised to schools across California had been delivered. County officials said distribution of the test kits from the state was just getting underway.

Those districts without their own stockpile were out of luck.

Other school systems have been discussing what actions to take in the coming weeks.

The Burbank Unified school board on Sunday held an emergency meeting — before deciding against a delay to Monday’s reopening.

Instead, officials are considering mandatory coronavirus testing for students and staff and requiring a vaccine booster for all employees by April 1. Officials also plan to post a Friday update to the community with testing results, provide parents and employees with contact information for those with questions and concerns, meet with labor groups and update masking policies.

Maria Castro, who’d given her husband Lysol for Christmas in lieu of cologne, also wondered about the weeks ahead for her daughter at Long Beach Poly.

“Do you think classes will be cancelled?” Castro asked her 18-year-old daughter, Sophie Villegas.

“I haven’t heard anything,” Sophie responded.

Not far away at Whittier Elementary, Miriam Morillo recounted her son’s response to how he felt about returning to class.

“Good — and bad because I’m not protected,” he told her. “I can get infected by the other kids.”

She told him to trust in God and also signed him up to get vaccinated on Friday.

Times staff writer Colleen Shalby contributed to this report.