(AP) — Mask requirements are returning in some school districts that had dropped them. Some are planning to vastly ramp up virus testing among students and staff. And a small number of school systems are switching to remote learning — for just a short while, educators hope.

With coronavirus infections soaring, the return from schools’ winter break will be different than planned for some as administrators again tweak protocols and make real-time adjustments in response to the shifting pandemic. All are signaling a need to stay flexible.

“Change has been the only constant in this fight,” Newark Schools Superintendent Roger León wrote in a notice to parents before winter break. He announced Thursday that students will learn remotely for at least the first two weeks of the new year. The virus, León said, continues “to be a brutal, relentless and ruthless virus that rears its ugly head at inopportune times.”

Long after the widespread closures in the pandemic’s early days, school and elected leaders say they are using the lessons and tools of the past two years to try to navigate the latest surge without long-term shutdowns, which had woeful effects on learning and students’ well-being.

In Florida’s Miami-Dade County, where one in four people were testing positive for the virus, the school system announced Thursday that all employees, volunteers and visitors will be required to wear face coverings at schools and facilities, and students will be strongly encouraged to wear them.

A state law prevents school districts from imposing mask mandates for students.

To help keep as many students in school as possible, the Centers for Disease Control and U.S. Education Secretary Miguel Cardona endorsed test-to-stay in December as an alternative to the previously recommended 10-day quarantines. Hundreds of schools have adopted test-to-stay policies for students who have had contact with an infected classmate.

“The goal remains to keep all schools open for in-person learning five days a week throughout the 2021-22 school year and beyond,” Cardona said in a message to schools marking the halfway point of the academic year. He said 99% of schools were open in-person in December, compared with 46% last January.

In the nation’s largest school system, New York City, 2 million at-home test kits provided by the state will be used to increase testing following the break, officials announced this week. Students whose classmates test positive can keep coming to school as long as their at-home tests are negative and they don’t have symptoms.