Los Angeles’s first teachers’ strike in 30 years disrupted classes for a sixth school day on Tuesday, after overnight negotiations between the union and the second-largest U.S. school district produced no deal.

Classes have been disrupted for some 500,000 students after 30,000 teachers walked off the job demanding the Los Angeles Unified School District raise their pay, cut class sizes and the hire of more support staff such as nurses.

Negotiations continued for 21 hours through to 6:13 a.m.