Chicago Public Schools teachers lined up Saturday outside the Chicago Teachers Union’s new “strike headquarters” to collect “on strike” picket signs they plan to use at schools Monday morning if the union and school district haven’t reached a contract agreement by then.

Bargaining between the two sides resumed shortly after noon Saturday. A Chicago Public Schools spokeswoman said both board president David Vitale and the mayor’s deputy chief of staff for education, Beth Swanson, are at the negotiations. She said Swanson has been advising the mayor day to day on talks.

But union vice president Jesse Sharkey reiterated disappointment with the direction of negotiations. Sharkey said the union “really laid its cards on the table” and had a “frank discussion” with Vitale earlier in the week about the issues that separate the two sides.

“The offer they came back with was disappointing to say the least,” said Sharkey. He would not give any details about the union’s most recent proposals to the district or what the board offered, but said negotiators are willing to work “24 hours if necessary, up to the deadline, to get this done.”

“As long as there’s time, there’s always a possibility for resolution without a strike, and that’s what we’re working for. I personally have two kids in the Chicago Public Schools. I’m not looking forward to Monday and having them not in school,” he said.

Sharkey spoke at a press conference where community groups and other unions spoke in support of teachers and urged the two sides to come to an agreement.

Expanding on the idea that a strike would be disruptive to students, Amisha Patel, director of the Grassroots Collaborative, said current conditions are disruptive.

“I’m talking about the disruption of not having air conditioning, or not having libraries in their schools.…When CPS closes their schools instead of investing in the schools, that’s what’s disruptive to students. And when CPS forces students in classrooms with 35 or 40 other children, that’s what’s long-term disruptive for our children.”

Tom Balanoff, president of SEIU Local 1, said thousands of city school janitors represented by his union will be wearing red kerchiefs Monday in support of teachers if educators do walk off the job.

“Contractually, we won’t be able to honor picket lines, but I want everyone to know that SEIU stands with the teachers,” Balanoff said. He called teachers’ demands “fair.”

The Chicago Tribune has reported that the union’s last known proposal was for a 19 percent pay hike in the first year of the contract. The Board of Education offered teachers 2 percent raises over four years. This week, union president Karen Lewis called that proposal “unacceptable,” partly because it wipes out automatic annual “step” raises teachers receive for added years of experience.

Step increases are common in teachers contracts and have been around in Chicago for some 45 years, but increasingly they are being called into question. Critics say districts should find ways to reward their best teachers, rather than offering all teachers additional money for added experience.

Erica Clark, founder of the group Parents for Teachers, says it’s not only about a raise for teachers.

“It’s about so much more, because the teachers are fighting for things that really matter in our schools. They want smaller classes. Parents here will tell you—35, 40 kids in a class! That’s just unacceptable. But you don’t hear the president of the board, you don’t hear Mr. Brizard talking about how they’re going to use this contract to bring smaller classes to the schools. That’s key.”

Clark blasted the board of education’s $25 million strike contingency plan to keep 144 schools open with non-CTU employees. The school district is offering students breakfast, lunch and “productive activities” at sites around the city. Chicago Public Schools spokeswoman Becky Carroll says 5,000 students have signed up to attend church and community group “Safe Haven” sites the board is paying for.

South Side parent Tanisha Sanders called the situation frustrating. She stopped at Brownell Elementary Friday afternoon to ask where she might be able to leave her third grader on Monday.

“It’s better than nothing,” she said of the schools CPS plans to keep some buildings open. She says she’ll have to ask a cousin to pick her child up or look for a babysitter because the CPS program runs only until 12:30 pm.

Another parent at Brownell, Nicole Scott, said she’ll be out with teachers on the picket line. She says she wouldn’t send her sons, one in kindergarten and the other in second grade, outside the immediate neighborhood. “There’s too much shooting. There’s gang-banging and all that going on. I don’t know nothing about that school, so why would I do that?”

Chicago Public Schools declined to give any updates on how negotiations are going.