Rep. Gus Hawkins (D-Calif.) will be 83 this summer, but age has not dimmed the gentleman's eye for sham. On June 7 he led his House Committee on Education and Labor through a lively hearing on the subject of tests. He strongly suspects that many tests do more harm than good, and he may be right.

In school systems throughout the nation, and in many industrial areas of employment, tests have become a way of life. Schoolchildren are forever taking one test or another. Their teachers spend hours responding to studies of how they administer tests. By one estimate, mandatory testing consumes 20 million school days and costs more than $700 million a year in direct and indirect expenditures. The preparation and publication of achievement and aptitude tests is big business.

The skeptical Hawkins sees monkey business. He senses that too many tests are given, too much reliance is placed upon test results, and too many capable youngsters and prospective employees are irreparably damaged in the process.

In these heretical views he found support from Walter Haney, director of the recently published report of a National Commission on Testing and Public Policy. Haney told the committee that a three-year study of tests had concluded that while there is a vital place for testing, the practice has gotten out of hand. Many tests fail to measure innate talent, and many test results are essentially phony.

''Are we kidding ourselves?'' Hawkins asked. He was incensed over a reading test he had been studying. He wondered aloud about teen-agers who are simply not good readers. They take a test, they flunk the test, and thereafter they are categorized as failures. Discouraged, embarrassed, they are ''tested out'' of the system, even though they have the capacity to become good technicians. He thought it unfair to stigmatize up to 40 percent of eighth-graders as ''least proficient'' because they did poorly on a multiple-choice test of reading comprehension.

Rep. Donald Payne (D-N.J.) added a confirming anecdote. He recalled the case of a young woman who failed an intelligence test for a summer internship. On that basis she should have been disqualified, but somehow she was hired anyway. She proved to be such an excellent employee that she moved up steadily in the company and is now a superintendent headed for executive rank.

Walter E. Faithorn Jr., a Maryland businessman, testified on behalf of Friends for Education, a nonprofit watchdog group founded six years ago. He began by acknowledging that well-conceived and securely administered tests are ''absolutely essential'' as measures of scholastic accountability. That was the last kind word he had to say about tests. Otherwise, his group is ''sorely disenchanted'' by what they have discovered.

Among the things they have discovered is a form of cheating by which teachers ''teach the test.'' The object is to achieve a ''Lake Wobegon effect,'' named for Garrison Keillor's mythical Minnesota community in which ''all the children are above average.''

Faithorn supplied the committee with documentation. Seven states apparently have engaged in wholesale deception. In West Virginia, for example, pupils took the standard Comprehensive Test of Basic Skills. Amazingly, 58 percent of 11th-graders scored above the national average. This was amazing because West Virginia ranks fourth from the bottom in college entrance scores.

The Lake Wobegon effect also appeared dramatically in South Carolina, Georgia, Kentucky, Oklahoma, Arkansas and Tennessee. In the view of Friends for Education, ''all kinds of cheating is going on in respect to these tests, and we think the big, commercial publishers of these tests know it and look the other way.'' The principal victims of this scam, Faithorn charged, are the children, especially minority children who are led to believe they are doing well when in fact they are not.

Hawkins listened patiently to two witnesses who defended the standardized school tests, but he was not much impressed by their statements. He kept coming back to the unfairness that results from over-reliance upon test scores as such, and he wondered aloud if alternative methods of discovering and encouraging talents could be devised. His committee has no particular legislation in mind. Hawkins looks at tests and he smells something fishy. After 27 years on the Hill, he has developed a remarkably sensitive nose.