As students start picking up No. 2 pencils and filling in tiny circles on their standardized tests, a debate is bubbling around them.

While multiple-choice tests are quick and easy to grade, some educators say multiple-choice exams aren't testing everything students should be learning."There is a significant number of things deeply valued in our basic subject matter that can't be tested in multiple choice," said Lauren Resnick, director of the Learning Research and Development Center at the University of Pittsburgh.

Multiple-choice tests can help determine a student's factual knowledge and can tell a little bit about a student's ability to draw conclusions, she said.

However, she added, "if you want to know whether a child can write an essay, there's no way to find it out from multiple choice. If you want to know whether a child can figure out the solution, can develop a proof in mathematics and explain it, you can't do that in multiple choice."

Multiple-choice tests have been a mainstay in American education since the advent of the high-speed grading machine for them in the 1950s.

One reason for their popularity is that they're cheaper to grade than other types of tests.

Scoring one standardardized test, the Iowa Test of Basic Skills, costs about $2 per student, according to Steve Dunbar, co-author of the test and a professor of measurement and statistics at the University of Iowa. There are additional fees for more detailed analysis. (Utah schools use the standardized Stanford Achievement Test, which is administered in the fifth, eighth and 11th grades in each fall.)

Adding one 30-minute essay, which must be read by at least two people, and a third if the first two disagree, adds $6 to $8 to the scoring price per student, Dunbar said.

Essay tests are considered to be "performance-based tests," an education buzzword which means the test requires students to do something besides filling in a bubble or a blank to show deeper knowledge.

In recent years, test companies have developed optional tests with open-ended or essay questions, but they haven't sold as well as multiple-choice tests.

Maureen DiMarco of Riverside Publishing Co., which publishes the Iowa tests, contended that the open-ended tests hadn't provided much "different or better information."

Monty Neill of the National Center for Fair and Open Testing in Cambridge, Mass., thinks multiple-choice tests still carry a high price.

Neill considers the tests "a cheap way to give an illusion that the public knows what is happening."The price is the harmful effect on curriculum and instruction," he said, meaning that teachers spend more time on rote and low-level thinking material so that students can do well on tests.

Resnick also believes the impact of multiple-choice tests on curriculum can be "enormous."

If teachers believe the tests matter to the children, the schools and their jobs, they're "going to find ways to spend a lot of time on activities they think are close to multiple-choice items," she said.

Even the Iowa's Dunbar thinks more districts should use standardized essay tests because "there is an impact on instruction, and it sends a certain type of message."

Even so, he thinks the amount of information that can be gathered in a short time makes up for the shortcomings of the multiple-choice format.

However, he added, "people probably rely on our test too much and try to use it for things I don't design questions for."

He thinks it's "horrible" to use the tests to determine merit pay for teachers. Nor does he think it's appropriate to use them for grade promotion.

"Where I see Iowa tests used best is when they're used by local teachers to give them an additional source of information about individual strengths and weaknesses of kids," Dunbar said.

Ed Haertel, a Stanford University professor of education, said the multiple-choice standardized tests could be beneficial "as long as we don't put too much weight on the tests and make them into some kind of Dow Jones Industrial Average of education.

"The problem really becomes overinterpreting them or making the high test scores too much of an end in themselves," Haertel said, noting that the tests measured only limited information compared to what students need to learn.

A compromise approach is the New Standards Reference Exam. It is mostly open-ended, but it also includes 30 percent multiple choice from the Stanford Achievement Test, Ninth Edition, so that there are national comparisons.

Begun in 1990, New Standards - a joint project of the Learning Research and Development Center at the University of Pittsburgh and the National Center on Education and the Economy - first developed internationally benchmarked academic standards, then designed tests to measure them.

The test is available, however, only at three grade levels in math and English, and costs $10 to $12 per student per subject.