The second largest school district in the United States canceled classes on Tuesday for what could be a three-strike by 30,000 Los Angeles education support staff who are backed by a teachers' union that refuses to cross their picket line.

The strike in the Los Angeles Unified School District will disrupt education, meals, counseling and other social services for 565,000 students and their parents. It follows a six-day teachers' strike in 2019 and the coronavirus pandemic that closed classroom instruction for more than a year in 2020 and 2021.

The Service Employees International Union Local 99, representing bus drivers, custodians, cafeteria workers and classroom assistants, called the strike to begin at 4:30 a.m. Pacific Daylight Time (1130 GMT) after last-minute negotiations broke down on Monday.

The union, which said 96% of its membership had authorized the strike, is demanding a 30% salary increase plus a further $2 per hour for the lowest-paid workers, the Los Angeles Times reported.

The 35,000-member United Teachers Los Angeles is also walking off the job in support, saying it wants to bring educational workers out of poverty, reduce class sizes and ensure each school is fully staffed.

Los Angeles Unified Superintendent Alberto Carvalho told reporters on Tuesday the district was offering a 23% raise plus a 3% bonus and that "there are still additional resources to put on the table."

"We understand the frustration," Carvalho said, acknowledging that workers had been underpaid for years and offering to remain on standby around the clock in order to reach a deal to end the strike early.

Despite the strike, the school district will attempt to provide food services for hungry students, Carvalho said, advising parents to identify multiple alternatives in case some meal stations are overwhelmed. (Reporting by Daniel Trotta; Editing by Bradley Perrett)