Los Angeles teachers announced Wednesday they will strike Jan. 10 if they do not come to an agreement with district officials, a move that would shutter the nation’s second-largest school system and leave nearly 700,000 students out of the classroom.

“We’ve reached the point where enough is enough,” said Alex Caputo-Pearl, president of United Teachers Los Angeles, the union representing the city’s teachers. “We have watched underfunding and the actions of privatizers undermine our public schools for too long.”

The announcement is the culmination of 20 months of tense negotiations with district officials over issues including teacher salaries, class size, staffing and standardized tests. United Teachers Los Angeles has pushed the district to boost teacher salaries and to hire more teachers, nurses, librarians and other staff. The system said it cannot afford it.

The school system Wednesday said the California Public Employment Relations Board issued a complaint against the teachers union, charging that its officers were negotiating in bad faith.

“Los Angeles Unified does not want a strike — which only UTLA can authorize — because a strike would harm students, families and communities most in need,” the school system said in a news release.

The strike date gives three weeks to reach an agreement. Students are on winter break until Jan. 7.

At the heart of the dispute is a disagreement over the district’s financial health: Superintendent Austin Beutner said the school system risks becoming insolvent if it does not curb spending. But the union says deficits are not as large as administrators insist and that system officials are directing money to a rainy-day fund when many schools lack nurses and classrooms are overcrowded.

“Why is the district hoarding the money when the need is in the classroom right now?” said Arlene Inouye, the union’s secretary.

On Saturday, thousands of educators and their supporters took to the streets of Los Angeles to call for teacher raises and for hiring more teachers to reduce class sizes.

The strike announcement comes at the end of a year marked by a wave of teacher activism, with teachers in six states walking out of their classrooms amid rallies in state capitals to protest sagging wages and budget cuts that left schools in disrepair. It signals that teacher activism that shuttered schools in West Virginia, Oklahoma, Arizona, Kentucky, Colorado and North Carolina is poised to continue in the new year.

But California stands apart, because earlier teacher walkouts occurred largely in GOP-led states where a combination of plummeting oil revenue and substantial tax cuts forced lawmakers to reduce school budgets. Many of those states have right-to-work laws that severely undermine the power of teacher unions, giving educators few tools to fight for wages, benefits and classroom resources.

In contrast, California teacher unions are among the most powerful political forces in the state, and Democrats have long held majorities in both legislative chambers.