The top education official in Washington State said teachers could face investigation and schools could lose funding - if the number of students refusing standardized tests keeps rising.
Washington superintendent Randy Dorn doesn't like the phrase "opt-out."
"It's really a refusal to take an assessment that's required by the federal government," Dorn said.
He said low participation rates could cost schools federal money.
Critics say the Smarter Balanced exams are too long, complicated, and difficult. At one Seattle high school, every student expected to take the test, refused.
Superintendent Dorn suspected teachers were part of a "stealth campaign" against the exams. He issued a warning.
"There could be an investigation to see if teachers did encourage not to take the test - and that to me, is an ethics violation, a code of conduct violation, and a teacher could be disciplined," Dorn said.
Dorn said few students are refusing to take the tests in eastern Washington.
Copyright 2015 Oregon Public Broadcasting