New York City schools have been temporarily blocked from enforcing a vaccine mandate for its teachers and other workers by a federal appeals judge just days before it was to take effect.

The worker mandate for the nation’s largest school system was set to go into effect Monday. But late Friday, a judge for the 2nd U.S. Circuit Court of Appeals granted a temporary injunction and referred the case to a three-judge panel on an expedited basis.

Department of Education spokesperson Danielle Filson said officials seeking a speedy resolution by the circuit court next week.

“We’re confident our vaccine mandate will continue to be upheld once all the facts have been presented, because that is the level of protection our students and staff deserve,” Filson said in an email.

She said more than 82% of department employees have been vaccinated.

While most school workers have been vaccinated, unions representing New York City principals and teachers warned that could still leave the 1 million-student school system short of as many as 10,000 teachers, along with other staffers, such as cafeteria workers and school police officers.

New York City Mayor Bill de Blasio has resisted calls to delay the mandate.