Like Wile E. Coyote convinced of his genius, Washington has vowed repeatedly that its latest schemes for reform will fix things “this time.” And, repeatedly, meaningful change has proved slippery.

Case in point: the “Every Student Succeeds Act” (ESSA) of 2015. Lawmakers on both sides of the aisle promised the new regulations would give schools more “flexibility” under the regulations and room for “innovation.”

Parents and teachers had been clamoring for relief from rules imposed under the George W. Bush-era No Child Left Behind (NCLB) law. Among other things, NCLB requires the U.S. Department of Education to score public schools according to annual test results in math and reading.

Families and schools got fed up with what they considered overtesting, and parents started keeping their children home on test day in protest. In 2015, nearly one in five New York students didn’t show up on test day. In Colorado, one in 10 failed to show.

Enter ESSA. Washington assured families that the new law would change things. Now one state may put those promises of greater flexibility to the test.

In 2016, Arizona lawmakers enacted legislation that allows traditional and charter school leaders to choose the standardized test they think best fits each school’s teaching methods. No longer would every school have to administer the same state test to all students. Over the next two years, Arizona’s Board of Education is scheduled to approve a menu of tests from which schools may choose.

Tests on the state board’s menu must meet or exceed state academic standards. They must also produce results that allow comparisons with other schools. For example, national norm-referenced tests allow for comparisons with students around the country. Tests such as these will be important to include on the menu.

Local education officials have a voice in the new approach as well. If a school finds an assessment that better matches its teaching methods, it can ask the education department to add that test to the menu.

“When schools are already offering a test from the menu that’s better aligned with their curriculum, they’ll be spending less time testing and more time with their students,” said state Rep. Paul Boyer, the Republican chairman of the Arizona House Education Committee and a high school teacher himself.

School leaders agree. “All schools, but schools of choice particularly, are well served by implementing tests that accurately measure the quality of that school’s curriculum and program,” said Peter Bezanson, CEO of BASIS, a charter school network that includes some of the top-performing high schools in the U.S.

“Similarly, it is a complete waste of time and resources for a high-quality school to implement tests that are not actionable for them,” he said.

Cal Baker, superintendent of Vail Unified School District and a member of the Arizona Board of Education, says the menu can also help “alternative” students — those who are on the verge of dropping out or dealing with teen pregnancy, for example.

“We have a tremendous level of difficulty getting our alternative education students to take the state test seriously,” Mr. Baker notes.

Because Arizona’s law is different from the federal requirement of one uniform state test, Washington’s reaction to Arizona’s law may be an indicator of just how much flexibility federal officials are prepared to grant states under ESSA. To date, federal officials haven’t weighed in on the law.

The Arizona menu of tests helps change a school’s focus from student performance on one test to decisions about how to meet student needs. As for parents and their children, boycotting tests doesn’t help students. Parents and teachers can help children better when they know the subjects that are giving students trouble.

The U.S. Department of Education officially encourages states to “push the field of assessment forward through innovation” under ESSA. Arizona’s menu of tests might be just the nudge that federal policymakers need to give key decision-making responsibilities back to states and schools.