Los Angeles teachers walked out on students Monday in a massive teachers strike over pay and benefits for educators, though schools remain open with substitute teachers.

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United Teachers Los Angeles union president Alex Caputo-Pearl contends educators are “in a fight for the soul of public education.”

Roughly 34,000 UTLA members took to the picket lines throughout the city early Monday, with some descending on the nearly 900 campuses in the nation’s second largest school district and others gathering at city hall or marching on Los Angeles Unified School District headquarters, KTLA reports.

The strike leaves about 600,000 students with substitutes hired by the district to keep schools open until district and union officials resolve the strike, which centers on pay raises and staffing. Negotiators with UTLA and LAUSD have been bargaining over a new contract for nearly two years, and both sides held press conferences on a dreary Monday to address the situation.

LAUSD Superintendent Austin Beutner told reporters the strike is impacting students in some schools more than others. Early childhood programs and preschools, for example, were not open Monday.

“Some schools are well-attended, some schools are less well-attended,” he said. “With a day like today with rain, we’re monitoring very carefully the impact to the areas in the north San Fernando Valley.”

Beutner told KCAL the goal is “to have a normal day at school.”

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Students will “be fed, they’ll be greeted by the same principal that greets them every morning at the door, and they will be learning,” he said.

Teachers and other school employees, meanwhile, are chanting and threatening other educators who dare defy the union.

“These subs crossed our picket line,” Deanna Cambell posted to Twitter on Monday, along with a photo with a list of substitutes working to keep schools open.

Pictures posted to the social media site and others show UTLA members decked out in red, toting signs in front of schools that read “Austin Beutner is the enemy of public education,” “Fund Our $chool$,” and “On Strike For Our Students.”

UTLA President Alex Caputo-Pearl is leading the first strike in over three decades over what he described as “woefully inadequate” contract proposals from LAUSD. The union has demanded a 6.5 percent retroactive raise, “fully staffed” schools with more nurses, librarians and counselors, and to slow the district’s embrace of independent charter schools, KTLA reports.

The union has also demanded class size caps and pointed to a $1.86 billion reserve the district has already dedicated to other uses to fund its demands.

LAUSD has offered to add 1,200 teachers, counselors, nurses, and librarians; vowed to limit class sizes to 35 students in middle school and 39 students in high school; and offered a 6 percent raise and backpay for the 2017-18 school year, according to the news site.

The district’s last offer included roughly $24 million in spending over the previous offer, a change tied to increased state education spending announced last week, KCAL reports.

UTLA officials contend it’s not enough.

“Here we are on a rainy day in the richest country in the world, in the richest state in the country, in a state that’s blue as can be – and in a city rife with millionaires – where teachers have to go on strike to get the basics for our students,” Caputo-Pearl said.

Beutner pointed out that a fact finder has already ruled that if the district were to meet all of the union’s demands, LAUSD would be bankrupt within two to three years. LAUSD officials also explained why the district can’t spend it’s $1.8 billion reserve, which is already earmarked to fund teacher retirements and other costs tied to the UTLA contract.

“School budgets in California are set in three-year increments, and from July 2018 to June 2021, Los Angeles Unified will spend $24 billion educating students,” according to a prepared statement. “This includes its entire, existing $1.8 billion reserve.”