Chicago teachers began a planned strike Thursday morning after many unsuccessful attempts to reach a deal regarding contract negotiations.

Almost 25,000 Chicago Public Schools (CPS) teachers started picketing early Thursday after months of negotiations between the Chicago Teachers Union (CTU) and CPS failed to reach a deal regarding teacher salaries, benefits, and better tools for their classrooms.

A statement by the CTU read:

After more than 10 months of frustrating bargaining, over 25,000 CTU teachers, clinicians, teaching assistants and support staff are officially on strike as of today, Thursday, October 17 … Educators are fighting for conditions that include smaller class sizes, adequate staffing — from social workers and school nurses to librarians and teachers for English language learners and special education students — and living wages for paraprofessionals.

However, Chicago Mayor Lori Lightfoot said Thursday that although CPS had just recovered from a “pretty significant crisis,” it did not have unlimited resources.

“But having said that, we put very generous offers on the table both for teachers and support personnel and I’m hopeful that we’ll be able to bring them back to the table and resolve all the other open issues,” she concluded.

Administrators and non-union staff members showed up to school on Thursday to serve meals even though classes were canceled for the city’s 400,000 students due to the strike.

Mayor Lightfoot also visited with the children of families who have been affected by the strike.

Although the city has offered teachers a 16 percent pay raise over five years, the union continued to demand a 15 percent raise over three years.

Additionally, CTU President Jesse Sharkey said the lack of staff had directly impacted students.

“Our schools don’t have (librarians), and we’re trying to teach kids to do well on reading tests,” said CTU President Jesse Sharkey.

First-grade teacher Victoria Winslow stated she was joining the strike because she could not step into a role that someone else might fill.

“I’m striking because class size does matter. Our support staff deserves a livable wage, and we only have a nurse one day a week — are we supposed to stop teaching and become nurses?” she concluded.

Despite the strike, negotiations resumed on Thursday morning, according to ABC 7 Chicago.