No one knows for sure how much a system of required state high school exit exams would cost, but the Pennsylvania State Education Association yesterday issued estimates of what it would cost just to help students who fail the exams to prepare to retake them: $112 million to $187 million a year, which it says is "conservative."

That's not counting the costs of developing and administering the 10 exams, which the state Department of Education has estimated at $5 million per test for development and $4 million per test each year for administration. The exception is an Algebra 2 test, which would be made available through a consortium.

Nor does it count the roughly $40 million a year it already costs for the current Pennsylvania System of School Assessment tests, given in grades 3 through 8 and 11 in math and reading as well as selected grades in writing and, beginning this year, science.

On Thursday, the state Board of Education unanimously approved a plan to require students to pass five of 10 end-of-course tests before graduation, beginning in 2013-14.

The tests are Algebra 1, Algebra 2, geometry, biology, chemistry, literature, composition, American history, world history and civics and government.

Students could be exempted from some of the tests by passing the PSSA or doing well on Advanced Placement or International Baccalaureate tests.

School districts could develop local assessments, but they would have to be "independently and objectively" validated by an approved outside vendor.

The vote is not final. The proposal now is in the regulatory process, which includes reviews by the governor, the attorney general and House and Senate education committees, plus public comment and publication in the Pennsylvania Bulletin.

Meanwhile, both the PSEA, the state's largest teachers union, and the Pennsylvania School Boards Association are concerned about how much the plan will cost and who will pay for it.

"PSEA believes it is irresponsible to proceed with this until the question of actual cost of the graduation exams -- how much and who will pay for it -- has been addressed," Wythe Keever, PSEA spokesman, said in an e-mail yesterday.

Harris Zwerling, PSEA assistant director of research, estimated it would cost $187 million to provide remedial classes just for math and reading if the class size were 15. It would be more than $112 million if class size were 25. Those are rough estimates, in part because the way remediation is provided varies widely, from one-on-one tutoring to classes to after-school programs.

Mr. Zwerling made the calculation figuring that nearly 63,000 students score below proficient in math and nearly 47,000 in reading in 11th grade.

He noted the estimates cover only math and reading, not the other tests.

"I think my estimates are conservative," he said.

Tim Allwein, assistant executive director for governmental and member relations for the Pennsylvania School Boards Association, didn't have an estimate, but said, "The cost of developing the tests and verifying them and keeping them fresh is going to be substantial. Not only is there not a clear estimate of the cost, but there's not a clear knowledge of who's going to pay for it."