NEW YORK (AP) — The nation’s largest school district can immediately impose a vaccine mandate on its teachers and other workers; after all, a federal appeals panel decided Monday, leading lawyers for teachers to say they’ll ask the U.S. Supreme Court to intervene.

The city’s Department of Education said the mandate would now go into effect at the end of Friday, so that all teachers and staff would be vaccinated by Oct. 4, the following Monday.

The three-judge panel of the 2nd U.S. Circuit Court of Appeals in Manhattan issued a brief order late in the day that lifted a block of the mandate that a single appeals judge had put in place on Friday.

After an adverse ruling from a Brooklyn judge, a group of teachers had brought the case to the appeals court, which assigned a three-judge panel to hear oral arguments Wednesday. But the appeals panel issued its order Monday after both sides submitted written arguments.

Attorney Mark Fonte, who brought the lawsuit on behalf of teachers and others, said in a statement that he and attorney Louis Gelormino were immediately petitioning the Supreme Court to intervene.

“As of this moment, the mandate is in place,” he said, adding that he and Gelormino were “dismayed and disappointed by this turn of events.”

Fonte added: “With thousands of teachers not vaccinated, the City may regret what it wished for. Our children will be left with no teachers and no security in schools.”

The city’s Department of Education said in its statement, “Vaccinations are our strongest tool in the fight against COVID-19 – this ruling is on the right side of the law and will protect our students and staff.”

In August, Mayor Bill de Blasio announced that about 148,000 school employees would have to get at least a first dose of the COVID-19 vaccination by Sept. 27. The policy covers teachers, along with other staffers, such as custodians and cafeteria workers.

The practical effect of the mandate was that teachers and other employees would have been unable to work, beginning Tuesday, if they had failed to get vaccinated.

As of Monday, 87% of all Department of Education employees have been vaccinated, including 90% of teachers, de Blasio said.

But United Federation of Teachers President Michael Mulgrew said a survey of some of its members found that only a third thought their schools could open without disruption.

“The city has a lot of work before it to ensure that enough vaccinated staff will be available by the new deadline,” he said in a statement.

Lawyers for teachers argued Monday in papers submitted to the 2nd Circuit that teachers who are placed on unpaid leave because they have not complied with the order will be irreparably harmed if the appeals court failed to block the mandate.

The lawyers wrote that the city’s order will “leave teachers and paraprofessionals without the resources to pay rent, utilities, and other essentials. The harm is imminent.”

They said the mandate would leave thousands of New York City children in the nation’s largest school district without their teachers and other school workers.

“Imminent and irreparable harm exists,” the lawyers insisted.

On Sunday, the city submitted written arguments to the appeals court, saying the preference by some teachers “to remain unvaccinated while teaching vulnerable schoolchildren is dwarfed by the public’s interest in safely resuming full school operations for a million public school students and ensuring that caregivers citywide can send their children to school secure in the knowledge that sound safety protocols are in place.”

City lawyers said courts have long recognized that vaccination mandates do not spoil the constitutional rights to due process that workers enjoy and have rejected similar challenges for over a century.

“Put bluntly, plaintiffs do not have a substantive due process right to teach children without being vaccinated against a dangerous infectious disease,” they wrote. “The vaccination mandate is not just a rational public health measure, but a crucial one.”