CHICAGO (CBS) — Chicago teachers voted overwhelmingly in favor of authorizing a strike, their union announced Thursday evening.

Chicago Teachers Union President Jesse Sharkey said the 94 percent of the teachers had voted in favor of authorizing a strike. This does not mean a strike is certain, and negotiations continue.

The earliest possible walkout date would be Oct. 7.

Educators and Chicago Public Schools officials have been negotiating pay and staffing shortages, among other issues.

CTU wants a 15% raise over a three-year contract. The district’s latest offer is a 16% total raise over a five-year contract.

Meanwhile last month, the Chicago Teachers Union rejected an independent fact finder’s contract recommendation, setting up a possible strike if they cannot reach a deal with CPS.

The recommendation that the union rejected involved an offer to boost pay checks – specifically a 16% pay increase over five years. Teachers are asking for more than money.

They want smaller class sizes, and more special education teachers, social workers, and librarians. Four or five years ago, CPS had 400 librarians, and next school year the district will have only 108, Sharkey has said.

Mayor Lori Lightfoot said Tuesday that she had heard the unions’ concerns about a lack of special ed teachers, counselors, nurses, and other support staff, and added, “That’s why we have baked those into the budget for this year.”

“There’s absolutely no reason why we shouldn’t get a deal done, and as I said last week, we will double, triple track, seven days a week, to get it done,” Lightfoot said.

If a strike did go ahead, it would be the first since 2012.