The scores of Arlington County students on 1985 standardized tests rose slightly in more than three-quarters of the test categories, remaining well above national averages, according to results released by school officials yesterday.

The Virginia Department of Education requires 4th, 8th and 11th grade students to take ability and skills tests in reading, mathematics, language arts, use of reference materials, social studies and science. In addition, 11th graders take a test of applied skills.

Arlington, like Fairfax and Falls Church, also tested second and sixth graders. "I am especially pleased with the progress shown at every grade level, particularly in the 11th grade," said Superintendent Charles E. Nunley.

Although the 11th graders' scores were the lowest of all grades tested, they showed the most improvement over last year, rising four to six percentile points in eight of nine categories.

As in previous years, students in each grade tested scored higher in mathematics than in any other category. The highest math score was for sixth graders, ranking in the 88th percentile of students nationwide.

Approximately 75 percent of all second, fourth, sixth and eighth graders scored above the 50th percentile, the national average, in all categories. About 65 percent of 11th graders scored above the national average.

The lowest score in Arlington was on the 11th grade social studies test, in which students ranked in the 63rd percentile.

The composite scores for basic skills tests of reading, math and language arts were:

Second grade -- 89th percentile; fourth grade -- 82nd; sixth grade -- 83rd; eighth grade -- 75th; 11th grade -- 72nd.