CNN — A union representing 30,000 Los Angeles school custodians, cafeteria workers, bus drivers and other support staff has started a three-day strike with support from the district’s teachers, effectively stopping classes for more than a half million students in the nation’s second-largest school system.

Members of Service Employees International Union Local 99 marched in the cold, predawn rain Tuesday, carrying signs reading, “I voted to strike for quality schools, better lives!” and “We keep schools safe respect us!”

The union wants “equitable wage increases, more full-time work, respectful treatment, and increased staffing levels for improved student services,” it said. Workers’ average salary is $25,000 a year, and most work part-time – which has led to staffing shortages, the union said.

Custodian Jose Tovar said his wages keep him beneath the poverty line. “We’re not asking for the world but just … to live above water,” Tovar told CNN affiliate KCBS/KCAL.

The district was shut down by a six-day strike in 2019, when the teachers union demanded smaller class sizes, more school staffing and higher wages. It followed a wave of strikes across the country, spurred by dismal school conditions and teachers working several jobs to pay their bills.

Now in Los Angeles, the strike is impacting students and families. Parent Jenna Schwartz understands the union’s decision, she said.

“We have some of our most underpaid workers doing some of the most challenging jobs on our campuses,” she told CNN affiliate KABC. “They’ve been negotiating for years, to no avail.”

But parent Mike Bernstein worries about the effects on his children, he said.

“Ultimately, I feel that they are probably being left behind in a battle between adults,” he told KABC.

The demands and the offers

The strike comes after nearly a year of unsuccessful negotiations with the Los Angeles Unified School District. Superintendent Alberto Carvalho on Monday said classes would be canceled starting Tuesday after last-minute negotiations – which included new raise offers – failed.

Members of the Los Angeles schools’ support workers union said they want:

• A 30% pay raise, plus an additional $2 an hour over next four years

• Increased employment hours for part-time workers

The latest offers announced by the Los Angeles school district on Monday included:

• A 23% recurring pay increase, plus a 3% cash-in-hand bonus

• A $20-an-hour minimum wage

• Full health care benefits for those working at least four hours a day.

United Teachers Los Angeles – a union representing about 30,000 teachers, is participating in a solidarity strike this week and joining the support workers union rallies – it said.

Workers ‘struggle to feed our own children’

Union members say they understand the challenges families face when schools shut down for strikes. Many of the workers are school district parents, too.

But “we need to make a living wage,” union member Adrian Alverez told CNN affiliate KCAL.

“We live in this weird paradox as workers that help feed children and yet we struggle to feed our own children,” he said. “We help students go to college, yet we don’t have enough money to send our kids to college.”

Max Arias, executive director of the local school support workers union, hopes the strike will help mitigate the daily struggles endured by workers – and students, he said.

“As LAUSD parents and workers, SEIU Local 99 members know a strike will be a sacrifice but the school district has pushed workers to take this action,” the union leader said in a statement.

“Families have been sacrificing for far too long on poverty wages. Students have been sacrificing for too long in school environments that are not clean, safe or supportive for all.”

The district will offer families help by opening 24 grab-and-go food sites and having 154 schools provide student supervision. Another 120 city-run sites at libraries, recreation centers and other locations will help supervise children, Carvalho said.

The Los Angeles Zoo is also offering free admission for students due to the closures. And its all-day zoo camp program for students in kindergarten through 5th grade added two free “extended care” hours per day.

‘We should not be depriving our students,’ superintendent says

The school district has tried to negotiate in good faith, said Carvalho, the superintendent.

“Under California law, we cannot drive the school system into a bankruptcy position. We cannot drive the school system into a red position. And if we were to acquiesce to all the demands, that is exactly where we would be, that is not legally allowable,” Carvalho told CNN.

“We are eagerly awaiting on a counter proposal and we are ready to put another compelling offer on the table to continue the dialogue.”

If the three-day strike continues as planned, it would be “virtually impossible” to keep schools open in the district of more than 500,000 students.

“We should not be depriving our students of an opportunity to learn,” Carvalho told CNN.

But the head of the education workers union said the strike might be the only way to force change.

“If the district doesn’t realize that our members are valuable … once they stop working, then nothing’s really gonna change,” Arias said. “Ultimately, what we’re seeking is improving the schools – equity in schools. That’s what we’re seeking.”

CNN’s Nick Watt, Taylor Romine, Camila Bernal and Sarah Moon contributed to this report.