Standardized test scores for black students in Alexandria public schools lagged behind those of white students by an alarming margin of as much as 48 points in the 1984-85 school year, prompting school Superintendent Robert Peebles to release the breakdown of scores by racial group for the first time.

"It's time to be open and less defensive about the problem," said Peebles, who is scheduled to hold a news conference today to release the scores of the standardized Science Research Associates test. The Washington Post obtained an early copy of the scores. Peebles said yesterday he will make raising black and minority test scores his top priority.

The disparity between the scores of blacks, who make up 47 percent of the school population, and whites, who account for 37 percent, is believed to be greater than in any other Washington suburban jurisdiction.

Of nine grades tested, the average difference between the races in composite scores for reading, math and language arts was 37 points. In Prince George's County, recent scores on a similar test, the California Achievement Test, showed a disparity of 20 points. On July 29, Prince George's School Superintendent John A. Murphy announced a program to battle the problem.

Alexandria School Board Chairman Lou Cook said yesterday that the city's schools must take a hard look at the reasons why its black, Asian and Hispanic students test significantly lower than white classmates.

"It's a problem we haven't talked about because nobody wants to be considered racist," Cook said. "But we have to identify the problem and set up a plan of attack."

Alexandria's 11th graders had the largest gap in the scores of black and white students. Their composite scores for reading, math and language arts tests put whites in the 75th percentile of students nationwide and blacks in the 27th percentile.

In grades one through eight, black students trailed white by between 29 and 42 points.

"Blacks and minorities start out behind, without all the goodies of white, middle-class kids, and it's hard for them to play catch-up," said School Board member Nelson Greene Jr. Greene, along with other black community leaders, attended a special breakfast meeting yesterday where Peebles informed them of the test results.

"What you see in Alexandria, you see across the country," said Harold L. Hodgkinson, a senior fellow at Washington's Institute of Educational Leadership. "In rural Mississippi the white scores are as low as the black scores in Alexandria. It's an economic factor, a matter of access to information."

Greene said he believed the Alexandria school system was doing "a pretty good job" of educating blacks and minorities, but said he believed the SRA tests are often unfair. "The verbal tests are based on the way nice, white, middle-class kids talk, not the way black kids talk. The test needs to be made fair," he said.

The racial breakdown also included Asian and Hispanic students in the city. The average composite score for 11th grade Asian students, who represent 8.2 percent of the school population, was 50. For Hispanics, who make up 7.5 percent of the students, it was 42.

Generally, the scores showed that blacks, Asians and Hispanics did better in math tests than in reading or language arts.

Both Peebles and Cook said Alexandria's SRA test results are actually more indicative of the divisions between poor and affluent children than of divisions by race.

It is not known how many of Alexandria's black students fall below the poverty level, but the city's average black family earns $14,700 a year, the lowest average for blacks in the metropolitan area, according to figures from the Washington Metropolitan Council of Governments.

In addition, 34.4 percent of Alexandria's 10,415 students are eligible for free or subsidized lunches, compared to 27.2 percent in Arlington and 6.5 percent in Fairfax, Virginia State Department of Education numbers show. That eligibility is based on family income level, and Alexandria school spokeswoman Dorothy Mulligan said yesteday that the overwhelming majority of students eligible for free or subsidized lunches are black.

Peebles said affluent families -- most of them white in Alexandria -- have higher expectations for their children, enroll them in nursery and other preparatory programs, coach them at home and provide the "elusive factor of motivation."

While it might take five years to see any significant narrowing of the gap in scores, Peebles said there will be a new emphasis on training teachers to deal with minorities, enlisting community support for directing reading projects, correcting homework and improving the teacher-student ratio in remedial programs.

Using a track metaphor, Hodgkinson said school systems in Virginia -- and other states that recently raised educational standards -- in essence took a five-foot high-jump mark, raised it to eight feet and "forgot to give the blacks and minorites who couldn't hit the original mark extra coaching help."