For the second time in five years, classes were canceled Tuesday for approximately 420,000 Los Angeles public school students after tens of thousands of service workers, backed by the powerful teachers union, went on strike.

Custodians, cafeteria workers, bus drivers, special education assistants and other members of the Service Employees International Union Local 99 walked off the job and hit the picket lines in the rain Tuesday morning after negotiations with the Los Angeles Unified School District came to a standstill. The 30,000 members of the service employees union are demanding higher wages and better working conditions.

The labor action is the first major work stoppage for the city's public schools since a 2019 strike by the 35,000 members of the United Teachers Los Angeles Union.

The teachers union is honoring the service union's picket lines, forcing the school district to shut down schools.

Cecily Myart-Cruz, president of the UTLA, said Tuesday that her members are supporting the service employees' demands to show "respect to the education workers that keep our schools working and our children safe."

"We stand in solidarity with them, recognizing that their struggles are our struggles ... that the only way we achieve our goals is by standing collectively together," Myart-Cruz said.

The service workers union has called for a three-day strike.

Hopes of avoiding a strike were dashed on Monday when a new effort to jumpstart labor negotiations broke down at the last minute, officials said.

"Despite our invitation for a transparent, honest conversation that perhaps would result in a meaningful solution that would avoid a strike, we were never able to be in the same room or at the same table to address these issues," LAUSD Superintendent Alberto Carvalho said in a statement.

Carvalho said he and the district's negotiating team waited for hours on Monday to resume labor talks, but never got a response from the service workers union.

"We've run out of time," said Carvalho, adding that he is still hopeful that negotiations will resume soon.

Max Arias, executive director of the service workers union, said the union had agreed to "enter a confidential mediation process" with the LAUSD.

"Unfortunately, LAUSD broke that confidentiality by sharing it with the media before our bargaining team, which makes all decisions, had a chance to discuss how to proceed," Arias said. "This is yet another example of the school district's continued disrespect of school workers. We are ready to strike."

Conrado Guerrero, president of the local service workers' union and a building engineer for the school district, said Tuesday that the "LAUSD has pushed us to a strike."

“I showed up every day, I installed air filters in classrooms and other facilities. My work was essential for student health," Guerrero told ABC News. "But it seems LAUSD has forgotten that.”

The service employees have been working without a contract since June 2020.

"We're not getting an equitable wage to feed families, have housing," Fatima Grayson, a striking special education assistant, told ABC Los Angeles station KABC. "A lot of people that do work for LAUSD have to work two jobs."

In December 2022, the union declared an impasse in negotiations, prompting the appointment of a state mediator.

The service workers' union said many of its members earn "poverty wages'' of $25,000 per year and are demanding a 30% pay hike, with an additional pay increase for the lowest-paid workers.

Carvalho said on Monday that the school district had upped its most recent offer to a 23% wage increase, along with a 3% "cash-in-hand bonus.''

Los Angeles Mayor Karen Bass said the city is helping parents cope with the strike by making recreation centers available to students. All city public libraries will also remain open and the Los Angeles Zoo is offering free admission to students during the strike.

Many parents said they are standing behind the service workers, including some who plan to walk the picket line with the striking employees.

"We have some of our most underpaid workers doing some of the most challenging jobs on our campuses," parent Jenna Schwartz told KABC. "The majority aren't receiving health care. They've been negotiating for years to no avail."

Rep. Adam Schiff, D-Los Angeles, joined service workers on the picket line Tuesday, saying he is supporting "all those who take such good care of our kids who are there in school."

"I stand here with people of Los Angeles who believe that those that have these important responsibilities should not have to live in poverty," Schiff said. "The median income of our bus drivers and our cafeteria workers that are school age is $25,000 a year. Those are poverty wages. People with some of the most important responsibilities in our schools should not have to live in poverty."

ABC News' Flor Tolentino contributed to this report.