SACRAMENTO, CA - Two recent events underscore the importance of improving the way we measure student achievement. The first was a front-page New York Times story that cited an American Federation of Teachers (AFT) study that said that charter school students often performed worse than comparable students
in regular public schools. The second was the release of California's 2004 student test scores.

Charter schools are deregulated public schools that promise better results in exchange for their greater freedom from bureaucratic red tape. There are more than 400 such schools in California. Because charters emphasize higher student achievement, the AFT finding that charter-school fourth graders performed half a year behind other public-school students on national reading and math tests is disturbing. The AFT study, though, has a crucial Achilles heel.

The study's conclusions were based on test results from a single year. In other words, it was a snapshot of student performance at one point in time. This static picture fails to show any achievement growth trends. This is especially important given that many charter-school students performed poorly at their previous schools and thus start at a very low level of achievement. A charter school may improve a student's performance, but that improvement won't be picked up if only a snapshot is used. The same problem was also on display in the
release of California's 2004 test scores.

The test scores showed that only 30 percent of third graders were proficient in English language arts. However, 45 percent of fifth graders were proficient in English. The Los Angeles Times reported that, "Educators were at a loss to explain the robust fifth-grade results, saying they expected the second and third grades to do better because of smaller class sizes and easier material to master.'' This befuddlement arises because a static picture is being used to compare the wrong things.

Instead of comparing today's third-grade scores with today's fifth-grade scores, which compares the performance of different groups of students, the scores of individual fifth graders should be compared with their own third-grade scores. That comparison would allow policymakers to see whether a student was growing in achievement.

Because of the snapshot problem, California should adopt a value-added assessment system that collects individual student test results over time and uses the results to determine how much a school or even an individual teacher has contributed to the improvement or decline in a student's performance. The state has taken a first step in this direction by assigning identification numbers to students so their performance can be
tracked.

The Pacific Research Institute recently proposed a new value-added model that calculates a rate of expected academic change, or REACH, using an individual student's test scores to come up with an annual individual improvement target for that student. In other words, given a student's current location on the ability scale, the REACH model tells teachers, principals, parents and officials how much a student's achievement needs to grow each year in order to be proficient in a subject area by the time each leaves school. Schools can then be judged on whether students hit those targets or not.

If the top goal of our education system is to improve student achievement, then we need to use a measurement device that gauges that improvement. It's time to create a value-added assessment system.

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Lance T. Izumi is a senior fellow in California Studies at the Pacific Research Institute in San Francisco. He can be reached via email at lizumi@pacificresearch.org.