The Scholastic Aptitude Test was about to begin and Colin Brown, an Alexandria high school senior, was nervous. "I screwed around a lot my first two years so I've got to do well on this," he said. "I really want to go to college."

An elegantly dressed Carl Anderson, 18, a senior at Washington's Woodson High School, was surprised and annoyed to learn that he would have to sweat through the grueling SAT in order to study fashion merchandising at New York's Fashion Institute of Technology. "I don't see what that test has to do with fashion," he said.

Standardized tests, the branding irons that have divided a generation of Americans into the sheep and the goats on a vast range of subjects, are under major attack in the schools, in Congress and in the courts.

Jeff Schatz, 17, waiting to take the SAT at T.C. Williams High School in Alexandria said he had taken a vocabulary cramming course the previous week. With a "C" grade average and an ambition to be physicist, he said, every additional right answer is precious.

Many students have paid up to $275 for coaching courses from firms that make a business out of preparing students for standarized tests. Brown, Anderson Schatz and 800,000 other college helpfuls sweating over the three-hour SAT are only a small part of the population that go through these peculiar rites of passage into our merit-conscious society every year.

Critics now are asking whether standardized tests truly measure the merit they claim to require, and they want to know who tests the testers. After an initial howl of injured privacy, the testers are beginning to come clean.

"There is nothing under the rug," said E. Belvin Williams of the industry leader, the Educational Testing Service in Princeton, N.J. "And we're going to prove it."

By standard industrial measures, the testing business isn't much. There are about 400 companies, but the top 10 do 90 percent of the testing. Even though 90 percent of all adults have undergone some kind of standardized test, the largest firm, ETS, took in only $94 million last year.

By other measures, however, such as the amount of fear inspired or influence cast, testing is big business indeed.

Test critics charge that:

Tests have invaded every corner of American life, but they are often assumed to define intelligence competence and potential in areas they were not meant to cover. Testers do little to curb these abuses.

Test scores brand people. Yet they may be a product of a sleepless night or a lucky day. Coaching may improve aptitude test results, which would make the test meaningless.

The public knows little and is told less about the way test questions are made up, validated and scored. With correct answers kept secret, there is no way to challenge apparently irrational questions.

Tests have contained racial, sexual and cultural bias that automatically classifies blacks and other minorities as goats.

There are now national, standardized computer-graded tests of the multiple choice variety to take in order to become a golf pro, an insurance or real estate sales agent or an auto mechanic, as well as to get into college or any kind of graduate school, the civil service or the foreign service.

There are tests to become a teacher, to get out of high school with a diploma or to avoid being labeled mentally retarded. And there are dozens of highly specialized tests within any number of professions.

Surveying the testing industry last month, the American Psychological Association found that all but the dozen large firms are "made up of one or at most a few persons who publish one or at most a few tests" while working as teachers, consultants or counselors on the side. "Beyond the professional time needed for the production of a test . . . to obtain volunteered subjects," the study continued, "a modest outlay for printing puts one in business."

The survey suggests that these cottage operations may deserve more criticism than the big firms that draw most of the fire.

The largest, and somewhat unfairly the norm by which the others are judged, is the Educational Testing Service, more than three times the size of its nearest competitor, the American College Testing Co. of Iowa City, Iowa.

The nonprofit ETS works largely on a contract basis, putting together and running tests for organizations that want to measure some group. ETS does the Scholastic Aptitude Test on 1.2 million high schoolers each year for the College Board, an association of 2,500 colleges and universities. It does the Law School Admissions Test (LSAT) for the Law School Admissions Council, and a stockbroker qualifying exam for the New York Stock Exchange.

In fact, there are almost 200 clients for whom ETS measures a total of 8 million people every year, employing 2,300 people in eight branch offices to do it.

Most of the drive for "truth in testing" is aimed at ETS. "They're exempt from income taxes and beyond the reach of the Federal Trade Commission or Justice Department anti-trust action or consumer protection law," said Alan Nairn, author of an upcoming study of ETS for consumer advocate Ralph Nader. "They behave like a corporation when they want to keep their internal operations secret, but like a nonprofit foundation when that helps."

ETS fought hard against passage in New York this year of a law that will require all testing organizations to make public beginning Jan. 1 any test questions and answers used in the state. It also led the opposition to a bill sponsored by Rep. Ted Weiss (D-N.Y.) that would require the same thing nationwide.

The House measure lies smothered in committee but may be resurrected next spring, especially if ETS holds to what appears to be a new line. "Students should see their test answers," said Williams in an interview. "We know it will pose operating problems, but we have the brainpower to solve those problems."

ETS got most of the higher education establishment to agree in House hearings that disclosure would hurt test quality by requiring the test makers to come up with entirely new questions every time the test is given. In New York, 20 to 26 testing programs have already been canceled by their sponsoring companies, and although ETS will continue to operate there, it will reduce the times it offers the SAT and cut back on special sessions for the handicapped.

Six states now have legislation pending to regulate standardized tests: California, Colorado, Florida, Maryland, Ohio and Pennsylvania. ETS' main competitor, American College Testing (ACT), would have to rethink all its programs should the Ohio law pass, according to Shannon Janes, ACT's chief of planning and coordination.

That is because ACT uses Ohio scores on its aptitude tests as the base of its equating procedure, the method that makes a 500 score today equal to a 500 score 10 years ago. ETS uses a complex mix of old and new questions for equating purposes on its aptitude tests, and agrees with Janes that making old test questions public will make the process harder.

"If we have to prepare four or five times as many tests as we do now, it'll be a production line and that's not possible with the methods we use now," Janes said. "Now it takes 2 1/2 years to build a new test form that's worth anything."

But Janes and ETS' Williams, among other industry figures, agree that their critics' pressures for change are good for the business in the long run.

"It's the best thing that's ever happened to us," said Sydell T. Carlton, part of a special ETS committee finding ways to implement the New York law. "There's a lot of turmoil here now, but it's created a climate in which changes not related to disclosure can get a hearing. All our procedures are getting looked at again."

It is clear, she continued, that some colleges and organizations use the scores in ways they shouldn't, and ETS may not have done all it could to discourage that. Many law schools, for example, don't even look at applicants with LSAT scores below a certain level, even though ETS literature constantly says that scores should be only one element of a selection process.

"There's a school of thought that says we should identify people who'll be good lawyers and help them go to law school." said ETS President William W. Turnbull. "That's an appealing model but it breaks down when you try to define a good lawyer. Is it a pro bono type or a magnificent defender of the cartel?"

Better, he said, to continue predicting only how well the student will do in law school, which is all the LSAT ever claimed to do.The SAT in its mountain of print also claims only to predict freshman college performance. iBut somehow both tests have come to mean more than that. It is as though colleges, students, their parents and everyone else think ETS in only being modest when it protests.

"This score will determine what colleges I can or can't go to," said Colleen Casey, 17, of Bowie, Md., the day before she took the SAT. "Sure, the colleges use other things, but they give this a lot of weight." A College Board survey of 2,600 found that 60 percent of the "very selective institutions gave the SAT "a great deal" of weight.

With so much at stake, Casey planned only to get a good night's sleep before the test. Other students pay up to $275 for cram courses from one of several dozen businesses that together served about 300,000 college-bound seniors last year, according to the Federal Trade Commission.

The FTC's Boston office compared two coaching schools and found that "underachievers" raised their test scores consistently, some by as much as 100 points. But the Washington FTC downgraded that to 25 points and the survey has been roundly criticized for its methods. Still, critics say that any coachability at all invalidates aptitude tests that are supposed to measure innate ability.

Wrong again, the testers say.

"It's a myth that you'll ever get a test that measures genetic potential of something unaffected by experiences a person has had," said ETS' Turnbull. "The SAT measures a developed ability to solve problems in terms of words or numbers. And that's very much a learned ability."

Coaching that focuses on vocabulary of long-term reading or brushes up on math skills is bound to help some, he added. If the student is disadvantaged at home and attends a bad school, it will show on the test. "There's no way to build into the test a measure of the opportunities the student had to learn the material," Turnbull said.

To blame the testers for scores among blacks that run 100 points below whites' scores is to shoot the messenger, Turnbull and others declared. If SAT scores correlate with family incomes, it may only show that the richer a family is, the more opportunities the children have. Tests cannot be blamed for showing where the problems lie.

But the critics are not satisfied. "That does not explain those blacks who do well in classes and perform adequately on all other measures except the standardized tests," said Susan Perry, an aide to Rep. Shirley Chisholm (D-N.Y.), in a test critics' seminar in Washington recently. Sponsored by De-TEST, a nonprofit group that says it wants to "De-mystify the Established Standardized Tests," the gathering included representatives of the 1.8 million-member National Education Association, the Parent-Teachers Associations and Ralph Nader's Public interest Research Group, among others.

Terry Herndon, NEA's executive director, wants to abolish all standardized tests. "They are similar to narcotics," he said. "They have a legitimate use but are widely abused."

The federal courts have focused on the racial bias issue, striking down a California IQ test used to place students in classes for the mentally retarded when a judge found "grossly disproportionate enrollments" of blacks in such classes. Another federal judge halted Florida's "functional literacy test" of high school pupils last year when he saw that 78 percent of all blacks failed, compared with 25 percent of the whites.

But the U.S. Supreme Court upheld South Carolina's use of the National Teacher Examination in certification and pay scales.

Clearly tests are not going to disappear. "We believe in tests as a way to show what a person has done and what they are ready to do next,' Turnbull said. "We've just got to do better in making them more accessible to people."