There was a carnival atmosphere in the Northern Virginia Special Olympics yesterday at Washington-Lee High School in Arlington. There were square dances and sing-alongs puppet and horse shows, and a soccer demonstration. Adrian Dantly gave the Special Olympics oath. Roy Jefferson acted as judge and presented awards and there was a gala opening parade and a sock hop for a finale.

And there were many winners among the more than 800 mentally handicapped contestants who participated in the games. Events ranged from track and field to gymnastics and swimming, with athletes from six counties and Alexandria competing.

Taking home three blue ribbons were the Wiggins brothers - Maurice, 14, Mike, 15, and Tyrone, 16 - from Herndon, who each won individual freestyle and butterfly swim events and joined Lewis Hembry for a junior-class 100-yard freestyle relay triumph.

Nine-year old Gary Gran of Ann Ludwig school in Woodbridge won his age division with a 9-feet-9 softabll throw. In the 16-17 division, Mike Scott of King George County won the boys 50-yard dash in 5.9 seconds, and Judy Carrick of McLean High nipped Martha Semidey of Edison in the girls 25-yard butterfuly swim.

Other winners were Charles Gregg of Fairfax in the 18-19 boys' tumbling (9.2 points) and Fairfax's Billy Payne in the same event (9.2) for 20-29-year-olds. Mary Smith of the Northern Virginia Training Center in Fairfax won the girls' floor exercises for 20-29-year-olds with 3.6 points, and Butch Purdue took first in the 30-and-over softball throw with a distance of 159 feet.