The nationwide emphasis on upgrading educational standards has involved rapid growth and serious errors for companies which score -- and write student tests.

Four companies dominate the market. National Computer Systems has jumped from only scoring tests to writing them also. Most of the standardized exams used in public schools are composed by Harcourt Educational Measurement, CTB/McGraw-Hill and Riverside Publishing companies.

• Over the past five years, the companies have expanded greatly -- with NCS, for example, enlarging its office space by 150 percent and expanding its presence from three states to 16.

• The new push for higher educational standards has meant greater public scrutiny of the companies, which used to hide behind a screen of bewildering numerical complexities, observers report.

• It has also meant greater publicity when mistakes are made -- such as when CTB incorrectly scored tests in New York City last year and sent thousands of students to summer school unnecessarily, or when Harcourt botched test scores in some California school districts last year.

• Experts say most of the test development work goes to just these three companies -- NCS having entered the field late -- because tests are expensive to design and produce and can be profitable only if they have large national markets.

Company officials say the rapid growth in testing has put a strain on their efforts to find more experts in the field, which is known as psychometrics.

They have also had to answer critics who claim that tests are a waste and rob students of good classroom teaching time. But spokesmen for the companies point out that the tests establish benchmarks and allow teachers to know where children are in the learning process.

Source: Jay Mathews, "Testing the Market," Washington Post, May 30, 2000.