With no deal over reopening to announce Friday night, Chicago Mayor Lori Lightfoot lit into the Chicago Teachers Union leadership, saying they “failed and gave us a big bag of nothing.”

Lightfoot also said she was still planning to open schools on Monday for preschool and special education students, as well as elementary school students. She said she expected teachers to be there for them. Teachers have vowed to remain working virtually until a deal is reached with the school district.

If teachers don’t come, Lightfoot threatened to take “further action” against them. But she said her team will stay at the table and try to get a deal. “Let’s get it done,” she said. She emphasized restarting in-person learning for preschoolers and special education students.

The mayor’s comments immediately drew reaction. A Chicago Public Schools source tells WBEZ the mayor’s remarks take progress made at the bargaining table “a step back.”

CPS CEO Janice Jackson, speaking at the same press conference as the mayor, did not go after the union. Instead, she repeated that she felt like a proposal that the school district put out on Wednesday was a foundation for an agreement.

The Chicago Teachers Union also said the mayor was not helping.

“Unfortunately, rather than build on the progress that has been made between our Union and the Chicago Public Schools bargaining team, Mayor Lightfoot is disrupting every possible settlement, compromise or partnership. The educators in the room were close to reaching an agreement. The boss stepped in at the 11th hour and blew it to pieces,” the union said in a statement.

The mayor scolded the union for not formally signing onto items they had agreed to. She said she gave them until 9 p.m. and the fact that they didn’t do it, created “chaos.”

Jackson also said the union isn’t taking note of research on school openings that indicate schools aren’t contributing to the spread of COVID-19. “The union leadership has chosen to disregard the science on reopening schools and instead replace CDC guidance with their own gut instincts.”

The union said that there was agreement on many issues with the school district, but that they were still pushing for a phased-in return tied to voluntary vaccination; baseline testing for students and staff; and accommodations for educators whose household members are at higher risk of COVID-19 illness and death.

Some 67,000 students are expected to return to schools on Monday. This includes elementary school students who would join preschoolers and special education students who resumed in-person learning on Jan. 11. This is just 32% of all students offered in-person learning, a figure that fuels the argument that even parents are not ready for it.

As Monday’s return date has drawn closer, the Chicago Teachers Union ramped up pressure for a deal over reopening. Last week, about 71% of members voted to refuse to teach in person until a deal was reached with their union. They did so with the understanding that if

Lightfoot and school district officials locked people out from teaching remotely, as they threatened to do, this could turn into a strike.

Some 12,300 teachers were required to report on Wednesday, but 85% did not. Yet, Lightfoot and Jackson held off on discipline and allowed staff to work remotely. They said they did want to see student learning disrupted by a strike.

But they were clearly upset that the union forced the district to cancel in-person classes for about 3,200 preschools and special education students who had resumed classes in buildings in mid-January.

The union and the school district have been at odds for months over returning to school, with the district pushing to go back and the union raising safety concerns. Union advocacy has already twice led to the delay of in-person classes and has gotten the school district to provide air purifiers for each classroom as well as air quality and ventilation reports for each school.

It also has gotten the school district to increase the amount of regular testing of staff and students. And when union members complained there was no plan for vaccination, three days later the school system rolled one out.

Sarah Karp covers education for WBEZ. Follow her on Twitter @WBEZeducation and @sskedreporter.