Faced with mounting and bipartisan opposition to increased and often high-stakes testing in the nation’s public schools, the Obama administration declared Saturday that the push had gone too far, acknowledged its own role in the proliferation of tests, and urged schools to step back and make exams less onerous and more purposeful.

Specifically, the administration called for a cap on assessment so that no child would spend more than 2 percent of classroom instruction time taking tests. It called on Congress to “reduce over-testing” as it reauthorizes the federal legislation governing the nation’s public elementary and secondary schools.

“I still have no question that we need to check at least once a year to make sure our kids are on track or identify areas where they need support,” said Arne Duncan, the secretary of education, who has announced that he will leave office in December. “But I can’t tell you how many conversations I’m in with educators who are understandably stressed and concerned about an overemphasis on testing in some places and how much time testing and test prep are taking from instruction.”

“It’s important that we’re all honest with ourselves,” he continued. “At the federal, state and local level, we have all supported policies that have contributed to the problem in implementation. We can and will work with states, districts and educators to help solve it.”