Thousands of teachers and other school workers have walked out in Sacramento.
The California capital is the second major U.S. school district this month to see a work stoppage over pay and staffing shortages.
In Minneapolis, teachers are in their third week of a strike.
The district said on Sunday that it made its "last, best, and final offer" as classes continue to be canceled for more than 31,000 students.
The walkouts come as schools across the country deal with the fallout from the coronavirus pandemic and limited resources for granting the demands of educators and support staff.
Across the country, union workers are seizing the opportunity posed by tight labor markets to recover some of the power they feel they lost in recent decades as unions shrank in size and influence.
And experts expect to see more labor strife as the country emerges from the pandemic.
The school district, which has 43,000 students, canceled classes Wednesday, the Associated Press reported.
On Thursday, the district announced classes were also canceled.
"While the next hours and days feel unpredictable for our children, families and staff, we will continue to support our students and their site leaders to meet basic needs while schools are closed for instruction and activities," the district said in a statement.