Resistance to standardized testing is spreading fast in Michigan and across the country. Parents in some suburban schools are discouraging their children from taking the Michigan Educational Assessment Program (MEAP) exam, and many educators and legislators are challenging the validity and value of the test. This is bad news for Michigan schools, especially for our most disadvantaged students. Statewide assessment is an essential part of any serious effort to improve academic achievement in our public schools.

Resistance to standardized testing is growing for three main reasons.

First, there is widespread anxiety about the use of tests as a basis for rewards and sanctions, for both schools and students. Schools fear the stigma of low scores, and the possible loss of state accreditation. Students worry about endorsed diplomas and the availability of scholarships if their test scores don't meet the standard.

Second, some parents are concerned that an excessive focus on standardized tests is eating up instructional time and causing educators to "teach to the test." Using a farmer's metaphor, some critics have pointed out that "weighing the pig doesn't make the pig grow." They claim that measuring what kids know may distract attention from the more urgent tasks of teaching and learning.

Third, there are technical problems with standardized testing. For example, no single test provides an accurate picture of what kids know. Measured scores fall in what may be a fairly broad range around a child's true score.

These are serious concerns that should be taken seriously. In our view, however, the concerns are dangerous if they are used to make the case against standardized testing. Instead, they should be seen as a compelling argument for the collection of additional and more precise information about how our schools and students are performing.

MEAP scores tell us that, when it comes to student learning, some Michigan schools are doing fine. But some schools are doing badly, and some are barely functioning. Without standardized testing to provide comparable information about schools, we could not make these judgments. The performance of our schools would be a mystery.

This lack of knowledge is unacceptable, especially in districts where parents do not have much objective information about how their schools and teachers measure up. The data on student achievement provided by the MEAP and other standardized tests are an essential diagnostic tool and a powerful incentive to improve performance.

MEAP does not tell us everything that we need to know about how schools and students are performing, because it only measures what students know at a single point in time. This is useful, but what we really want to know is how much students learn from year to year. What's the value added in our schools? To answer this question we need to test each child every year.

Many schools already perform annual testing, but to accurately assess our students' progress we need a statewide test that measures learning gains in a rigorous and comparable way.

We need to use standardized tests carefully, and resist the temptation to make summary judgments about schools and students on the basis of a single test score. We must also work to support educators and parents to ensure that all children have the opportunity to learn the material that is being tested. But-as any farmer will tell you-we also need to measure what children know, and how much they learn from year to year.

David N. Plank, Ph.D. is director of the Education Policy Center at Michigan State University. Michael David Warren, Jr. is secretary of the State Board of Education and the vice president of the New Common School Foundation.