Chicago’s teachers strike will move into a second day on Friday after City Hall and the Chicago Teachers Union failed to strike a deal but reported progress on a key issue: class size.

The district notified parents via robocall about 6 p.m. Thursday that it would cancel classes for a second day in the nation’s third largest school district. District officials said that about 7,500 students came to school Thursday — about 2.5% of enrollment — and that schools would remain open and minimally staffed Friday.

Union negotiators, appearing on Thursday at Malcolm X College after bargaining wrapped up for the day, reported little movement on two other top union priorities — increased staffing and support for special education students.

Mayor Lori Lightfoot, in a Thursday evening appearance on public TV station WTTW, said she was concerned that the union hadn’t shown “a sense of urgency to get a deal done.” Lightfoot said negotiators reached some minor agreements but for weeks haven’t discussed core issues like compensation, insurance, and benefits.

Lightfoot also called on the union to respond to the city’s contract proposals all at once, instead of bargaining in “piecemeal.”

“We made some progress on two issues: class sizes, I’m not sure where we are on staffing, but those have been the two issues that have been the topic of conversation when we actually have had bargaining,” the mayor said. “But there’s a lot of other open issues.”

The most progress did appear to come on class size. The union wants the district to agree to lower the cap on class sizes. The district has offered to give a committee that could enforce and fund measures to lower class size $9 million in discretionary funds. But the union said that isn’t enough to hire enough staff or find other solutions covering the proposed five-year contract for the 23% of district classrooms that it says are overcrowded.

Negotiators remain deadlocked over adding support positions such as nurses and social workers. The union wants the district to set minimum staffing targets, enforce those targets, and develop a plan to progress toward the union’s requested staffing levels. The union is still waiting for a counterproposal, its Chief of Staff Jen Johnson said Thursday night.

On special education, the union wants a written allocation of case managers for students with Individualized Education Programs, which lays out specialized services. The district has offered an allocation, and the union wants a larger one.

The union also is seeking additional prep time for elementary special education teachers who say they are burdened by complicated paperwork required for serving students. Instead, the district has suggested awarding stipends for special education teachers who take on extra work.

On Thursday, the union publicly surfaced a new demand: adding staff to finding housing and mental health support for homeless students. The city is offering to fund a homeless liaison position for every school with more than 90 homeless students, about 12 schools currently, but the union wants more staffing.

Besides teachers, on Thursday special education aides, bus aides and custodians represented by the SEIU also walked out over stalled negotiations with the district.

Teacher talks began on Thursday morning, broke for union leaders to speak at a midday downtown rally, and concluded around 6 p.m.

At schools around the city, teachers brought signs and wore red, as passersby honked car horns in support and parents brought doughnuts and urns of coffee. Some students even joined picketing and marches.

Catch up on what you missed during the day on our live blog here.