The average mathematics score of Fairfax County students taking standard college entrance exams last year rose five points over the previous year in contrast to an overall drop nationwide, school officials said yesterday.

Fairfax County students who took the Scholastic Aptitude Test (SAT) averaged the same on the verbal test as in the previous year. Nationally, average scores on the college board tests last year declined two points in both the verbal and math sections of the examinations.

Fairfax School Supt. S. John Davis said he was delighted with the latest scores and attributed them to the "emphasis we are placing in the areas of composition, spelling and math computation."

A special panel of prominent Americans recently concluded a two-year study of declining SAT scores. The panel blamed the decline on television, watered-down school standards, the increased number of blacks and women now taking the tests and social traumas that made the last 10 years a "decade of distraction."

Blacks typically score 100 points or more lower on the tests than whites, and women score considerably lower than men on the math tests.

The panel rejected the idea of ascribing the decline to changes in the tests themselves.

Dr. John Hurley, director of research and testing for the Fairfax County schools, said SAT scores declined in the county from 1971 until last year. Fairfax's average score on the verbal section of the exam was 473 (of a possible 800) in 1971, compared to 451 in 1975 and last year. County mathematics scores declined from 503 (also of a possible 800) in 1971 to 494 in 1975. The 1976 mathematics score announced yesterday was 499.

Since 1963, the average score nationwide on the verbal section of the exam has dropped 49 points from 478 to 429. Mathematics scores dropped 32 points, from 502 to 470.

SAT scores for other Washington area jurisdictions were not available yesterday.