LOS ANGELES (Reuters) - More than 30,000 Los Angeles teachers demanding pay raises and smaller classes walked off the job in America’s second-largest school system on Monday, marching downtown in the rain after negotiations over a new contract broke down.

Students arriving at some 900 campuses across the Los Angeles Unified School District (LAUSD) were met by their teachers carrying laminated picket signs in the city’s first teachers’ strike in three decades. The system serves roughly 640,000 students.

“It’s an existential battle for the future of public education,” teacher Mike Finn told Reuters outside John Marshall High School in the Los Angeles neighborhood of Los Feliz.

Some 20,000 teachers, union members and supporters gathered outside City Hall, carrying umbrellas in a rare Southern California rainstorm and chanting.

No end date has been given for the strike and the two sides have not met since union leaders said on Friday they were “insulted” by the district’s latest offer.

Officials for the LAUSD, which serves mostly working-class families who would lack child care if classes were canceled, kept schools open, staffed by administrators and substitute teachers.

“This morning, buses rolled and breakfast was served. Los Angeles Unified schools are open and providing every student with a safe and welcoming learning environment,” district officials said on Twitter.

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But attendance was down considerably as parents kept children home out of concern for their safety or to honor picket lines. Schools with limited staffing gathered students in gymnasiums to be supervised by a handful of administrators and substitutes.

The walkout follows a wave of teachers’ strikes across the United States over pay and school funding, including job actions in West Virginia, Kentucky, Oklahoma and Arizona. Denver teachers could vote to strike by Saturday if no deal on a new contract is reached by then.

TEACHERS SEEK 6.5 PERCENT PAY HIKE The strike by United Teachers Los Angeles (UTLA) marks one of the largest and one of the few targeting a Democratic-controlled government in a blue state. Los Angeles County officials say the union demands are unaffordable.

Los Angeles Mayor Eric Garcetti, a Democrat weighing a run for his party’s nomination in the 2020 presidential race, has largely avoided taking sides. In a video posted on Twitter, Garcetti urged the district and union to reach an agreement as soon as possible.

Union negotiators have demanded a 6.5 percent pay raise, more librarians, counselors and nurses on campuses, smaller class sizes and less testing, as well as a moratorium on new charter schools.

The district has countered with a proposed 6 percent salary hike with back pay and a $100 million investment to hire more staff and decrease class sizes.

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Teacher pay currently averages $75,000 in the LAUSD, according the California Department of Education.

Los Angeles County School Superintendent Austin Beutner said Friday’s offer to teachers was beefed up after newly installed California Governor Gavin Newsom increased education spending in his proposed budget.

“This impasse is disrupting the lives of too many kids and their families. I strongly urge all parties to go back to the negotiating table and find an immediate path forward that puts kids back into classrooms and provides parents certainty,” Newsom said in a written statement on Monday.

At a news conference on Monday, Beutner urged union negotiators to return to the bargaining table and said he had asked the mayor and governor to help broker an end to the strike.