[A version of this story was originally published in Chalkbeat New York.]

U.S. Education Secretary Arne Duncan said this week that the federal government is obligated to intervene if states fail to address the rising number of students who are boycotting mandated annual exams.

Duncan’s comments came a day before Gov. John Hickenlooper and two former Colorado governors publicly defended the state’s testing and accountability system and spoke against opting out of tests.

Testing has been a hot-button issue this year, as many Colorado districts are reporting higher-than-usual rates of students opting out of state standardized tests. This fall, approximately 83 percent of eligible Colorado students took 12th grade exams. Official figures for spring tests have not yet been released.

States across the country are also seeing more students and parents refuse to take standardized tests: In New York, an advocacy group reported that more than 15 percent of eligible test takers refused to take standardized English exams last week.

The trend has raised questions about the consequences for districts. Federal law requires all students in grades three to eight to take annual tests, and officials have said districts could face sanctions if fewer than 95 percent of students participate.

On Tuesday, when asked whether states with many test boycotters would face consequences, Duncan said he expected states to make sure districts get enough students take the tests.

“We think most states will do that,” Duncan said during a discussion at a conference of the Education Writers Association in Chicago. “If states don’t do that, then we have an obligation to step in.”

Duncan said that students in some states are tested too much, and acknowledged that the exams are challenging for many students. But he argued that annual standardized exams are essential for tracking student progress and monitoring the score gap between different student groups.

He also said the tests are “just not a traumatic event” for his children, who attend public school in Virginia.

“It’s just part of most kids’ education growing up,” he said. “Sometimes the adults make a big deal and that creates some trauma for the kids.”

Former Gov. Bill Owens, a Republican, said on Wednesday that while the state might currently have “too much of a good thing” (too many tests), he believes opting out is harmful to a system that is ultimately beneficial for students.

But Colorado’s state board of education passed a resolution in February saying that the state’s education department cannot penalize districts with low rates of student participation in standardized tests due to parent opt outs. And a bill that would protect parents’ right to opt students out of tests passed in the state Senate earlier this month.

A federal education department spokeswoman said last week that the agency could withhold funding from states if some of their districts have too few students take the exams, but that it has not yet done so because states have addressed the issue on their own.