After holding steady or rising for several years, average scores on college entrance examinations fell substantially last year in school systems throughout the Washington area.

The decline was greatest in Montgomery County, which dropped behind Fairfax for the first time ever in both the verbal and mathematics sections of the nationwide Scholastic Aptitude Tests.

Despite a significant drop, Arlington County continued to have the highest combined scores of any major school system in the area, but its class of 1979 was just one point above the average for Fairfax.

The decline was least severe in Prince George's County, but the county continued to be the only local system reporting scores below averages.

No scores were available from the District of Columbia. Its school superintendent, Vincent Reed, said his school system has not requested them from the College Entrance Examinations Board since 1975, when Barbara Sizemore was superintendent.

Reed added that he was requesting the scores now.

"Sizemore and her administration took a very, very dim view of testing," Reed said, "and she just obliterated the testing program. But I think we ought to know how our students are doing, and we're requesting those scores now."

The examinations, were given throughout the country to about 1 million college-bound high school seniors of the class of 1979, and are widely regarded as a key measure of academic abilities. Students may take the three-hour, multiple-choice tests as many times as they wish, but only the most recent scores for each student are used in computing the SAT averages.

Scores fell statewide last year in Maryland and Virginia, as they did throughout the country.

In Maryland the decline was substantially greater than the national drop -- a total decline of seven points on the mathematics and verbal tests combined, compared to a nationwide drop of three points. For the first time Maryland fell below the nationwide averages in both verbal and mathematics skills. The drop in Virginia last year was three points.

Maryland's scores still remain slightly ahead of Virginia's but the gap between the two has almost vanished. For the class of 1979 it was just three points, compared to a difference of seven points in 1978.

In 1972, students in Maryland averaged a total of 28 points above the Virginia average. The Maryland averages then were confortably above the national average while Virginia students were substantially below it. In the 1979 tabulations both states are slightly below the nationwide average.

Gerald Bracey, director of research, evaluation, and testing for the Virginia education department, said the was uncertain why Virginia's relative improvement had occurred. It may have happened, he said, because "we've had growth in Northern Virginia and Tidewater that's largely affluent people, and they're bolstering the scores."

Sheldon Knorr, Maryland state commissioner of higher education, said the decline of his state had taken place among the brightest students and the least able.

This year, he said, there were just about 2,000 students with SAT verbal scores over 600, compared to about 3,000 with such scores five years ago. The number with scores below 300 increased from 2,000 to 4,000 during the same time.

Scores range from 200 to 800 on each part of the SAT exam.

Even though it fell seven points last year, Fairfax County is the only local jurisdiction whose total average score for 1979 was as high as it had been in 1975.

The Alexandria total for 1979 was three points below 1975, although it had dropped nine points from 1978.

Compared to 1975, Montgomery fell 8 points, Prince George's 10 points and Arlington 24 points. The nationwide decline was 12 points in the same period.

The average 1979 SAT scores were as follows: (table omitted)