More than half a million public school students in Los Angeles could soon be impacted by a massive teacher strike as a bargaining impasse continues between the city’s school district and teachers union over class sizes, salaries and other issues.

More than 30,000 members of United Teachers Los Angeles had been slated to walk out of classrooms as soon as Thursday, NPR reported.

On Wednesday, the union said it would postpone the strike until Monday due to a disagreement over when and whether it had filed the right paperwork giving formal notice of its intent to strike.

If the walkout takes place, it’ll be the first teacher strike in the Los Angeles Unified School District — the nation’s second largest — in nearly 30 years. More than 600,000 public school students in 900 schools will be affected by the strike.

Rising power! Los Angeles is strike ready for our students! #StrikeReady #UTLAStrong⠀ pic.twitter.com/wZIH6TPeMK — United Teachers Los Angeles (@UTLAnow) January 9, 2019

Rising power! Los Angeles is strike ready for our students! #StrikeReady #UTLAStrong pic.twitter.com/oQ8dEHiIqJ — United Teachers Los Angeles (@UTLAnow) January 8, 2019

Negotiations have been dragging on for over a year between the teacher’s union and the LAUSD. Among the union’s demands include higher salaries, smaller class sizes and more support staff like librarians, nurses, counselors and social workers.

“We want an agreement that works for our kids ― that gets to a place where we’re not dealing with 50 kids in a classroom, where we’re not dealing with 40 percent of our schools having a nurse for only one day a week,” union president Alex Caputo-Pearl told CNN.

The two sides have struggled to reach an agreement. District officials say they don’t have sufficient funds to meet all the teachers’ demands — an assertion that union leaders have refuted.

“We have been in negotiations with LAUSD since April 2017. We have been working without a contract for almost one year,” the union said in a statement. “Even with $1.86 billion in reserves, LAUSD says it does not have the money to improve our schools.”

According to the district, schools will remain open, classes will continue and meal services will not be interrupted even if the strike occurs.

More than 2,000 reassigned administrators and about 400 substitute teachers will take the place of the striking teachers, the district said. It remains unclear, however, how effectively this plan can be executed.

“It’s case by case, school by school,” Shannon Haber, an LAUSD spokeswoman, told CNN of the district’s plan. “We’re going to have to troubleshoot on the day of.”

This story has been updated with news that the strike was postponed.