Not a single state adopted a new graduation-exam requirement in 2006, and one state even took a step back, abandoning plans to withhold diplomas for kids who failed the test.

In total, 22 states require students to pass a test to graduate high school, and three others are phasing in these ''exit exams'' by 2012. But no other states are close to joining in, said Jack Jennings, president of the Center on Education Policy, which released the study Wednesday.

''It shows that there's been a kickback against testing,'' Jennings said. ''And some states are pretty satisfied with their schools. They aren't lining up to follow the same policy.''

Even still, graduation exams remain an influential part of U.S. education. About two-thirds of the nation's 15 million public high school students are required to pass one.

But most of the tests don't cover a full high school education. To get a diploma in many states, students must only show they can handle 10th-grade level content.

In Idaho, the passing score is at 8th-grade level this year. The state plans to raise it.

Unlike testing under the federal No Child Left Behind law, in which testing is used to grade schools, graduation exams have personal consequences. And that can cause backlash.

Utah, meanwhile, was to start withholding diplomas this year. But the state changed course as it became clear how many students would be left behind, the study says. The state opted instead to note on a diploma whether a student had passed the graduation exam.

The states that use the exams generally run from New England to the South to the West Coast. ''It's the inner part of the country that's not affected,'' Jennings said.