RALEIGH - Significantly fewer public school students passed state math tests in 2005-06 due to tougher standards approved Thursday by the State Board of Education.

Students taking the end-of-grade math tests given in third through eighth grades will now have to correctly answer about half the questions to pass, compared with as few as a third of the questions on the old exams.

Students are not expected to answer all questions correctly because the tests purposely include questions well above grade level to help measure the skills of the state's highest-performing students.

The new standards were retroactively applied to exams taken this past spring, resulting in an immediate and dramatic drop in passing rates throughout the state. For instance, 92.3 percent of fourth-graders passed the old math exam in 2005 compared with 65.9 percent this year.

"It's what the state board has been talking about for the past year of having more rigorous standards," said Lou Fabrizio, accountability director for the state Department of Public Instruction. "It's 21st century standards."

The state will officially release individual school scores Nov. 1 under the school accountability program known as the ABCs of Public Education. Fabrizio said that the higher math standard will likely mean far fewer Schools of Excellence, a recognition given to schools in which more than 90 percent of the test scores are passing and the students are meeting academic goals set by the state.

Also Nov. 1, the state will release information on whether teachers will get bonuses based on how well their students performed. Fabrizio said the bonuses aren't tied directly to the math requirements, but fewer teachers are expected to earn bonuses this year.

For several years, the state has come under fire about whether the end-of-grade math exams are too easy to pass.

Critics had questioned how North Carolina students could do so much better on state-mandated exams than they do as part of a nationwide test known as the National Assessment of Educational Progress.

Fabrizio said the new passing rate will bring the two standards closer together. He said it made sense to make the change now because the state's new math exams are based on more rigorous curriculum.

Fabrizio said the state expects to get permission to lower the target math passing rate for schools under a different federal testing program that is part of No Child Left Behind. That program measures math and reading progress among groups of children by race, income and other factors.

Diane Villwock, director of testing and evaluation for Chapel Hill-Carrboro schools, said the changes will be painful at first but teachers will have to adapt. "We want the exams to accurately reflect student achievement," she said.