The percentage of Montgomery County ninth graders who passed the Maryland functional writing test rose by one point this year, but the passing rate among black students fell by five points and among Hispanic students by one point, according to new figures released by the school system.

The unexpected decline for blacks and Hispanics on the statewide writing test -- one of four tests that will be required for high school graduation -- is seen as a set-back to the board of Education's strongly stated commitment to improve minority student achievement.

The board had given outgoing school Superintendent Wilmer S. Cody a mandate to improve minority performance when he was hired in 1983. His handling of the issue was among the factors cited by some school sources for dissatisfaction with Cody, who is leaving his job next month.

Cody, who will be replaced by his deputy, Harry Pitt, is scheduled to present the board today with an updated plan to improve minority student achievement.

Board member Blair Ewing said he was "surprised and very depressed" by the decline in the passing rate on the writing test among blacks and Hispanics. "I think this is further evidence of how much time we've lost between 1983, when we committed ourselves to black student achievement, and now four years later," he said.

Ewing said the school system has failed to develop "specific strategies" to improve minority student test scores.

Overall, 83 percent of county students passed the test, compared with the state figure of 67 percent. In Montgomery County, the passing rate for Asian ninth graders improved eight points to 88 percent, whites improved one point to 85 percent, while blacks declined to 73 percent, and Hispanics to 69 percent.

The writing test will be required for graduation starting in 1989.

The last time Cody presented a minority plan, in February, some school board members and black community leaders said it was not aggressive or far-reaching enough and did not hold individual schools accountable for improving the scores of minority students.

Paul Scott, director of minority education for the school system, said he was puzzled by the decline in scores, and said a major part of the new minority plan will be to closely monitor the test scores of individual minority students from year to year.

Currently, the school system records only the scores of minority students as a group year by year and does not follow the progress of individual students.

"We're trying to get a handle on the same kids and how they have progressed," said Scott, who was hired a year ago to coordinate minority improvement efforts.

Schools that improve minority performance would be rewarded with certificates of achievement and money awards; schools that do not show improvement would "examine their program and teaching practices," according to Cody's report.

If the school does not show improvement within two years, a school team of central office staff members will be called in to determine what is wrong and correct the problem.

If minority achievement still does not improve, the area associate superintendent can reassign some school staff to improve the school's performance.

"I think (the minority plan) will need some refinement . . . but I think it's headed in the right direction," Scott said.

James Robinson, a Montgomery parent who is chairman of the Citizens Minority Monitoring Committee, a group of black parents who monitor minority issues in the school system, said he is shocked by the decline in black and Hispanic writing test scores. "I expected them to improve, even if not by quantum leaps," he said. "I am anxious to know what in the world went wrong."

Robinson, who has criticized the school system's insufficient progress with minority students, has long suggested that it keep better records on the progress of individual students and hold individual school principals accountable if minority achievement does not improve at their schools.