YUBA CITY, Calif. – About 700 Yuba City teachers walked out on students Thursday to prove to district officials they’re worth the 13 percent raise their union is demanding in contract negotiations.

Yuba City Unified School District Superintendent Nancy Aaberg told the Appeal-Democrat that school officials hired and trained substitute teachers “to provide a safe and engaging learning environment for the students as long as we need.”

Officials with the Yuba City Teachers Association and district have been negotiating a new union contract since the last one expired after the 2015-16 school year, and the YCTA has so far rejected six separate offers to increase pay, CBS Sacramento reports.

The YCTA argues that teachers in Sacramento, a much larger school district, are paid 33 percent more than Yuba City educators, so it’s holding out for a double-digit pay increase.

“For instance, the total maximum package for a first year teacher in Sacramento City Unified School District is $77,788, but for (a) Yuba City Unified School District teacher, it’s $58,466,” according to the news site.

“The district’s latest proposal included a 3.5% pay raise; but the teachers association is asking for 13%.”

The 13 percent raise stems from the YCTA’s assertion that YCUSD employees make 13 percent less than the state average, according to the Sacramento Bee.

Aaberg told the site the union rejected a district proposal to increase top teacher pay to $95,000 a year. The district simply can’t afford to increase pay across the board by 13 percent, she said.

YCTA president Dina Luetgens held a news conference in front of Yuba City High School on Thursday to make a grand spectacle of the union’s tantrum.

“This is both an economic strike in support of the YCTA’s fair bargaining demands and an unfair practice strike to challenge the district’s violation of California law,” Luetgens wrote in the union’s strike notice, according to the Appeal-Democrat.

District officials described the strike as “extremely disappointing, but … far from surprising” in a statement posted to the YCUSD website.

“It comes after nearly a full year of union leaders shunning the negotiations process in favor of forcing a confrontation that never had to occur,” the statement read.

District officials warned parents about the strike on Tuesday, and informed them that students are expected to attend class even if their teachers refuse to. The district will also continue after school programs as union teachers pace school sidewalks to chant and waive picket signs.

The strike follows a vote by about 85 percent of the union’s 700 members in May, of which 95 percent allegedly voted in favor of walking out on students.

Teachers will lose their pay and pension payments while they’re out on strike, though they will retain their health care coverage, the Appeal-Democrat reports.

The last contract negotiation session ended Aug. 24, and both district and union officials pointing at each other for stalling the process.

“It’s on the district to meet and resolve this,” YCTA bargaining head Steve Jennings said. “If you look at their last proposal, they’re not trying to resolve this.”

Aaberg said “the district stands ready to deliberate and negotiate at any time, but that would have to be initiated by the union at this point.”

The strike will impact about 13,300 students in 18 schools, and it involves teachers, speech and language pathologists, nurses, counselors and school psychologists represented by the YCTA, according to the Sacramento Bee.