Chicago teachers, clinicians and paraprofessional union members voted by a wide margin to authorize a strike, setting the stage for a walkout less than six months into Mayor Lori Lightfoot’s term. Educators could walk out as early as Oct. 7.

The union said 94% of its members voted in favor of a walkout.

With ballots in from 90% of schools late Thursday night, the vote meets the 75% threshold of support from all active union members required by state law.

“This is a clear signal from the members of the Chicago Teachers Union that we need the mayor and the Board of Education to address critical needs across our schools,” said union President Jesse Sharkey.

In a joint statement, Lightfoot and schools chief Janice Jackson said they had been bargaining for months “in a good faith effort to create an inclusive process” that took into consideration teachers’ concerns and ideas for improving schools. “We are committed to doing everything we can to finalize a deal that is sustainable for all Chicagoans and for our city’s future, that respects our teachers, and continues our students’ record-breaking success.”

The vote does not guarantee that teachers will strike, but the union can now announce a walkout date with 10 days’ notice. The union’s 700-member House of Delegates could vote on a proposed strike day at its next meeting on Oct. 2. 

Related: A tale of two strikes. What can Chicago learn from past walkouts? 

Meanwhile, negotiations will continue between the city and union. Sharkey said bargaining would resume on Friday. 

The teachers’ contract with the district expired June 30. 

Talks have stalled primarily over whether to write additional staff that the union is demanding into the contract or not. The two sides also haven’t agreed yet on class sizes, prep time, pay, health care, or the length of the contract. 

The district said it is has put a generous pay raise on the table — a 16% raise over five years for teachers. Both of the city’s major newspapers have editorialized in favor of the district’s offer.

In the joint statement from City Hall and Chicago Public Schools, the mayor and schools chief said that they had put forth a pay deal that would make Chicago teachers “among the highest compensated in the nation” and had committed to increasing support staff.

“As the product of public school systems ourselves, we know firsthand how hard our teachers work, and we celebrate their engagement and tenacity during the bargaining process over these past months,” Lightfoot and Jackson said.

When announcing the results Thursday, Sharkey said that the vote was not just about pay and benefits. “Pay and benefits alone are not enough, we care deeply about the learning and working conditions in our schools,” he said. Sharkey reiterated the union’s demands for class size limits and for the city to lock in firm numbers of nurses, social workers, and special education positions in the contract.

Related: #TrackingtheContract: Here’s what has happened in negotiations so far

Earlier in the week, Sen. Bernie Sanders attended a boisterous union rally in Chicago, helping bring national attention to the effort. The Illinois Federation of Teachers union issued a statement in support of the strike authorization vote on Thursday night.

During past teacher walkouts, the school district, park district, and YMCA have offered child care and free lunch for students affected by walkouts. 

Chicago could see at least three school-related strikes in October. Besides district teachers, educators at Passages charter school also voted earlier this month to authorize a strike. 

And Service Employees International Union Local 73, the union representing nearly 8,000 Chicago Public Schools support staff — whose work ranges from working with special education students to staffing metal detectors at school entrances — won a strike authorization vote last month. Those employees could also walk out in October, causing further disruptions at schools. 

During the city’s last contract negotiations with the Chicago Teachers Union, in 2016, observers saw a strike as all but inevitable. But district officials made several concessions at the last minute, averting a full-fledged strike. 

The city’s last full-fledged teacher strike was in 2012. That year, teachers walked off the job for the first time in 25 years.