The rates of school dropouts and grade retentions in Arlington County are higher for minority students than for whites, and black students are suspended at a rate nearly three times that of whites, according to a report from a committee that spent three months examining ethnic student achievement.

The committee recommended that improving the performance of all low-achieving students be a "high, long-range priority" for the School Board for at least five years.

"Band-Aid or piecemeal efforts will yield only limited, if any, success," the committee wrote in its report, completed last month. "The pattern of low achievement has developed over many years, and many years are needed to show improvement."

Superintendent Arthur W. Gosling asked the committee, comprised of staff members, principals and curriculum supervisors, to look at minority underachievement last fall, after standardized test results showed that the average scores of black students lagged behind those of whites by as much as 46 percentile points.

In examining statistics broken down by ethnic groups, including those on dropouts, grade retentions, suspensions and representation in gifted/talented programs, "We wanted to see if there were other factors that might contribute to low performance," said committee Chairman John L. Crowder, director of program assessment for the schools.

Figures on high school dropouts in 1984-85 showed that nearly 7 percent of Hispanic students dropped out, compared with 3.7 percent of Asian/Pacific Islander students, 3.4 percent of blacks and 2.8 percent of whites.

Retention rates for 1984-85, determined by comparing the number of students held back in all grades with that ethnic group's total population, showed that blacks were retained at the highest rate, 10.5 percent. Hispanic students had a retention rate of 8.1 percent, followed by 5.7 percent for Asians and 4.2 percent for whites.

Black students were suspended in 1984-85 at a rate of 10.2 percent, nearly three times the rate for white students and more than five times the rates for Hispanic and Asian students.

In addition, the committee reported that 83.3 percent of the 1,455 students identified as gifted and talented are white, 10.9 percent are Asian, 3.6 percent are black and 2.2 percent are Hispanic.

School Board Chairman Gail H. Nuckols said school officials have been aware of disparities among ethnic groups in test scores and other areas for several years. "I don't feel that we can feel comfortable that we've made very much progress," she said.

Several board members said that by concentrating on raising minority achievement, problems such as the dropout and retention rates would be affected indirectly.

"When you raise student achievement, students' expectations for themselves, student self-esteem, you are attacking discipline issues, dropout issues," said board member Dorothy H. Stambaugh.

Stambaugh said low achievers may lack academic support at home. "Maybe we just have to learn to provide some of those things" students miss at home. "We have to give some of those extra field trips, put books in those children's hands permanently, take them to the public libraries, provide after-school homework clinics."