SEATTLE (AP) — The first day of classes at Seattle Public Schools Wednesday was cancelled and teachers are on strike over issues that include pay, mental health support, and staffing ratios for special education and multilingual students.

“No one wants to strike,” Seattle Education Association President Jennifer Matter said. “But SPS has given us no choice. We can’t go back to the way things have been.”

Contract talks continued.

The district said in an email to parents that it was “optimistic the bargaining teams will come to a positive solution for students, staff, and families.”

Districts around the country have faced labor challenges as the pandemic put extraordinary stress on teachers and students alike. An infusion of federal stimulus money has helped stabilize school district budgets, and teachers unions have sought to improve pay, resources and and working conditions after a difficult few years.

High inflation, a national teacher shortage and the goodwill teachers earned from their pandemic-schooling efforts are all bolstering union efforts, said Bradley Marianno, an assistant professor of education policy at the University of Nevada, Las Vegas.

“By all measures, school budgets actually look pretty good right now,” Marianno said. “So as teachers union contracts are expiring, they’re looking for new deals that essentially send more funding to teachers and more funding to students.”

School in the Seattle suburb of Kent was supposed to start Aug. 25 but has been delayed as teachers there strike. Early Wednesday the union said it had reached a tentative agreement with the district.

Teachers in Columbus — Ohio’s largest school district — last week ended a brief strike, agreeing on a package that included 4% raises, includes plans for building improvements, reduced class sizes and innovative paid leave benefits.

In Denver, marathon bargaining sessions resulted last week in tentative agreement for an 8.7% raise for educators, a higher salary for first-year teachers, and more money from the district for health insurance costs.

Teachers in Minneapolis, Chicago and Sacramento walked out earlier this year before securing new contracts.

In Seattle, the school district has offered pay raises of an additional 1% above the 5.5% cost-of-living increase set by state lawmakers — far less than the union says it wants — plus one-time bonuses for certain teachers, including $2,000 for third-year Seattle teachers earning an English language or dual-language endorsement.

The union says it is opposing the district’s efforts to eliminate staffing ratios for special education students, saying that will mean more work for general education teachers and special education teachers alike. The union also says the district’s proposals would make general education teachers more responsible for supporting multilingual students.