The Tacoma school district says it may sue its teachers union if teachers continue their strike over contract negotiations.

The teachers strike has kept thousands of children out of classes for almost a week as the Tacoma Education Association continues pressing Tacoma Public Schools for an increase in salaries.

Strikes by public employees are illegal in Washington.

Angel Morton, the president of Tacoma’s teachers union, says teachers will resume work when the district agrees to pass money from a supplement state budget to educators.