The first day of classes for Kent Public Schools students will be delayed because educators are going on strike, district officials announced Wednesday evening.

Students were supposed to start the new school year on Thursday, one of the earliest start dates in the Seattle area, but the district and teachers’ union could not come to an agreement on a contract. Kent Education Association (KEA) members voted Monday night to strike if negotiations weren’t wrapped up by Wednesday.

“We are deeply committed to recruiting and retaining a high-quality workforce that serves to equip every student to be globally competitive in college, careers, and in life,” district officials said in a statement. “We remain in negotiations with the KEA and remain committed to reaching an agreement and starting school as soon as possible.”

The union is negotiating for more pay. It says its teachers need raises to stay competitive, and that they want manageable class sizes and more mental health support for students. KEA is also negotiating for what they describe as a manageable case load for staff working with English learners and students in special education.

Teachers and staff planned to show up at their schools on Thursday morning with picket signs.

Kent is one of the largest school districts in the greater Seattle area, with an enrollment of about 24,000 students last year.