Public school teachers in Jersey City, N.J., are striking after contract negotiations broke down in the early hours of Friday morning.

NJ.com reported Friday that teachers launched protests outside schools, with some of their students joining in. Teachers also reportedly blocked substitutes from entering schools.

The teachers — who are part of the 4,000-member Jersey City Education Association union — have been working under expired contracts since Sept. 1, according to NJ.com. They are demanding lower health-care costs as part of contract negotiations.

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"Quality, affordable health care is a fundamental right for everyone," Ron Greco, the president of the city's teachers union, said in statement. "My members are prepared to step up and take on this fight for everyone, knowing full well that it will be a long, difficult process."

The Jersey City Board of Education met Thursday night to try to reach a deal. That meeting stretched until 12:30 a.m. on Friday, with board members approving a contract offer, according to NJ.com.

But by the time the offer was approved, teachers had already been alerted to the strike.

The strike comes just 10 days after lawmakers in West Virginia approved a 5 percent pay raise for teachers in the state to end a nine-day strike that shuttered public schools.