For the first time, the College Board has publicly released the average scores of black and white students in its Scholastic Aptitude Tests. The gap between the two groups is wide.

On the verbal part of the SAT, the average score for blacks was 329 (of a possible 800 points), compared to 449 for whites. The differences was even wider in the mathematics section, on which blacks averaged 355 -- 135 points below the 490 average for whites.

The results, based on a 10 percent sample, are for college-bound high scholl seniors who graduated in 1977. They were given to a House Civil Service subcommittee studying federal employment exams, which show a similar difference in black-white scores.

Lois Rice, the College Board vice president who heads its Washington office, said the differences were "created by home environment, schooling, and economic conditions." For example, she said, almost 60 percent of blacks taking the SAT report a family income below $12,000, compared to just 14.5 percent of the whites. "Blacks do less well in the tests," Rice said, "because blacks have done less well than whites in the whole society. But there are some people who want to kill the messenger who gives the news."

Although some critics contend the College Board withheld disclosure of black-white scores because of bias in the tests, Rice said it was done "for just the opposite reason. We didn't want to give fuel to the people who say there are genetic differences in intelligence between blacks and whites and might use the results invidiously."

Sylvia T. Johnson, associate professor of search methodology at Howard University, said the low scores for blacks "certainly indicate some problems in achievement but there also is bias in the test."

Johnson, who recently published a book, "The Measurement Mystique," said, "There are a lot of things they try to do to avoid item bias [in individual test questions] but there are sources of bias that are hard to remove from tests. There are differences in educational levels, differences in motivation in test taking, differences in the outcomes that people see coming from the tests. I think the results should be used very cautiously."

Even though the scores for blacks are low, "they are not unexpected, unfortunately," said Thomas Sowell, a professor at the University of California-Los Angeles who edited "American Ethnic Groups," a study issued last year by the Urban Institute.

"Down through history," Sowell said, "there have often been these differences between different groups."

Sowell said wide test score differences exist between Catholics and Protestants in Northern Ireland, and between people from the remote Hebrides Islands and the rest of Scotland. In each case those from the higher-status, more-educated group score much higher, Sowell said.

In The United States, mental test data collected during the 1920s show well-below average scores for Polish and Italian immigrants. By the 1950s, both these groups scored above average, Sowell said, as they became assimilated and their socioeconomic status rose. Sowell expects a similar improvement to occur in test scores for blacks, though it may be delayed, he said, because of the poor quality of many big city schools they attend.

According to College Board Figures, the average scores for Washington public schools, which are over 90 percent black, are 326 on the verbal part of the SAT and 353 in math. These are close to the national averages for blacks.

"I'm afraid [the District] is part of a more general problem," said psychologist Kenneth B. Clark, whose studies were cited by the U.S. Supreme Court in its 1954 school desegregation decision.

"There is still a general neglect of the education of black children," Clark declared, "and the educators want to cover it up . . . I've argued with the College Board about things. They're not perfect, of course. No instrument is perfect. But the tests are like a thermometer that shows a disease. If you throw it away, the disease is still there.

"I think if we stopped the testing black children would be abandoned educationally even more than they are now without there being an indicator of the educational neglect."

The new College Board figures also show average scores for Chicano (Mexicano-American) students. Their SAT scores were well below those of whites but much higher than blacks, averaging 374 on the verbal part of the SAT and 412 in math.

Mexican-American taking the test also fell between blacks and whites in average family income as reported to the College Board.