Teachers at 19 Chicago charter schools will hold strike authorization votes next week that could open the door to the first-ever work stoppage at any charter school in the nation.

Votes will be cast Oct. 30 by teachers at the city’s 15 schools in the Acero network, the largest unionized charter operator in Chicago Public Schools. Teachers will vote Nov. 2 on a possible strike at four Chicago International Charter School locations: ChicagoQuest North, Northtown, Wrightwood and Ralph Ellison.

Charter school teachers united as ChiACTS have voted to authorize a few strikes over the last two years — including at Acero schools when the network was known as UNO — but this would mark their first strike vote since merging last year with the Chicago Teachers Union. More than 700 teachers could hit the picket line.

After their contract with Acero expired in August, union leaders say they’re pushing for pay raises, smaller class sizes and improved special education resources.

“If charter schools are going to be a part of the educational environment and landscape going into the future, we have to safeguard our future,” CTU president Jesse Sharkey said Wednesday outside Carlos Fuentes Elementary, 2845 W. Barry Ave. in Avondale, where dozens of teachers marched with signs and chanted ahead of an Acero board meeting.

In a letter sent to parents earlier this week, Acero said it has been negotiating since May, with the union most recently rejecting a proposal that would raise the average teacher salary by about 5 percent to $67,937.

“We are committed to providing a competitive compensation package to our teachers and staff,” the Acero administrators wrote. “We do so focused on the best possible educational opportunities for our students.”

The charter network claims the union’s position “could result in cuts to services, technology, programming and positions.”

Chris Baehrend, chair of the CTU’s charter division, slammed Acero executive officers’ six-figure salaries.

“This is not about a couple of bad employers. We’re out here to move the charter industry,” he said. “The charter model of innovation has been to pay teachers less, bust unions and line management’s pockets.”

The union says charter networks rake in 8 percent more funding per pupil compared to CPS rates, while charter teachers’ salaries are 30 percent lower — a claim that Illinois Network of Charter Schools president Andrew Broy called “erroneous.”

“The charter movement was founded on the principle that students need additional educational opportunities and a strike would do nothing to further such opportunity,” Broy said.

Teachers have never gone on strike at any charter school in the United States. In addition to UNO, teachers in Chicago have threatened strikes at ASPIRA and Passages charter schools since 2016, but deals were struck before classes had to be canceled.

The CTU now represents teachers at 34 charter schools since last year’s union merger.