A National Academy of Sciences committee yesterday strongly rejected charges that standardized tests discriminate against blacks, even though blacks on average score far below whites on almost all of the exams.

While the committee cautioned that the tests should not be the only factor in hiring or college admissions, it said the tests, if properly developed and interpreted, "can be useful predictors" of on-the-job performance and college grades.

Dropping such tests, as some civil rights advocates have urged, is not warranted by the evidence, the panel said, and could produce "lower productivity and worker morale." It criticized federal antidiscrimination efforts, which, it said, "have reached the point where even relatively good employment tests are being thrown out along with the bad."

The 19-member panel for the four-year study was headed by Wendell R. Garner, a psychology professor at Yale University, and included law professors, sociologists, and economists, as well as experts in psychology and testing.

The group said that a wide array of studies indicates that blacks and whites with similar test scores generally do equally well in subsequent grades and job performance.

Overall, it said, the tests "predict . . . performance as well for blacks as for whites." But it said a lack of discrimination in the tests "does not refute the claim" that there is discrimination in society and that the unequal test scores themselves may result from "unequal background and preparation due to low socioeconomic status and other factors."

As a result, the panel said the test scores should be "balanced" by measures of individual motivation and "support of demographic diversity" in making job and college admissions decisions. But the panel said it "strongly objected to fixed quota systems" as well as inflexible cut-off scores.

It warned, however, that standardized tests "should not be compromised in the effort to shape ethnic distribution" and questioned the workability of the consent decree under which the federal government promised to replace its PACE hiring exams with tests on which blacks and whites do equally well.

"Tests should not be required to do things they cannot do," said panel member Lyle V. Jones, a psychology professor at the University of North Carolina, "such as guarantee that distributions of scores will not differ for different racial or ethnic groups."

The panel reported that most American colleges accept nearly all applicants and suggested that except for highly competitive schools they should "reassess their ability test requirements since these may be unnecessarily expensive and inconvenient."

It said it found "no evidence of systematic abuse" by testing companies, such as the Educational Testing Service, as test critics led by Ralph Nader have charged.

Yesterday, Allan Nairn, author of the testing study issued by Nader in 1980, disagreed. The new report, he said, "basically toes the test industry line on all the major issues." Nairn, now a researcher with the Council on Hemispheric Affairs, said the panel "ignores major chunks of research" that the tests have "very low validity" and thus unfairly harm low-scoring blacks.