Accusing Democratic Mayor Lori Lightfoot of rejecting contract proposals that would create better public school conditions for educators and students, the 25,000-member Chicago Teachers Union went on strike Thursday to push for "pay and benefits that give us dignity and respect."

In addition to teachers, more than 7,000 teacher aides, security guards, and custodians—members of Service Employees International Union (SEIU) Local 73—will join CTU's strike.

The goal of the walk-out in the nation's third-largest school district is "to win—in writing, in an enforceable contract—learning and working conditions that respect educators and provide Chicago's students with the schools they deserve," the union said in a statement Wednesday night.

"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, some of whom earn less than $30,000/year," said CTU.

It's official. Rank and file strikers are telling the press why we're out on the picket lines tomorrow. #FairContractNow #CTUSEIUstrike #PutItInWriting pic.twitter.com/1ViBN6jAgm — ChicagoTeachersUnion (@CTULocal1) October 16, 2019

Classes for around 300,000 Chicago Public School students were canceled on Thursday in anticipation of the strike, which follows months of tense contract negotiations. Teachers and school workers are expected to begin taking to the picket lines at 6:30 am CT ahead of a mass rally and march in the afternoon.

Stacy Davis Gates, vice president of CTU, told reporters Wednesday that "our children deserve the best that this city has to offer."

"They do not deserve broken promises. Our South Side communities, our West Side communities are littered with broken promises, unkept commitments," said Davis Gates. "This contract has to represent something different for the city of Chicago—it has got to represent something different. And she ran to do that. Period."

Chicago-based writer Devin Schiff called the walk-out "one of the most significant strikes in years" in an article for the socialist magazine Jacobin on Wednesday.

"The most important aspect of the unions' strategy for the labor movement is their commitment to solidarity—not only with fellow members of their own union, but with another union, Local 73, as well as students and all of working-class Chicago," wrote Schiff.

"The CTU and SEIU draw direct lines from crumbling facilities and understaffing to policies of privatization and austerity, and take initiative in areas not traditionally seen as within educators' purview, like housing and immigration," Schiff added. "By doing so, they're showing how these factors all affect the educator’s capacity to teach and the student’s capacity to learn. Their case is unimpeachable."