Square dancers know what you think of them and they don't like it a bit.

"Square dancing is not square," insists Bob Spence of Silver Spring. "The kind of thing people remember from grade school is just not true. This is 1978 and it's very much updated."

"People are forever asking if you stomp your feet and carry a jug," complained a woman from Springfield. "They think it's like a Saturday night barn dance where everybody gets stone drunk.

"Or else they say, 'Oh, I took that in grade and I hated it.'"

Norm Jackson's teenage son worked out a way to deal with the square dancer's image problem: He leads a double life. "As much as he likes it," Jackson said, "he told me he hasn't burdened his friends on the wrestling team with the fact that he square dances."

Square dancing. At worst, the words conjure up images of barefoot, jug-toting, foot-stomping hillbillies; at best, a herd of aging suburbanites dressed up like a road company of "Oklahoma!"

Indeed, with their dancing duds on, square dancers don't exactly fade into the woodwork. The men sport Western-style shirts - plaid or gingham or prints - and string ties. The women tuck their feet into soft leather flats with ankle straps, and their figures into short skirts, cinched at the waist and wide . It looks like the Hourglass Figure of the Year awards.

But 5,000 to 10,000 Washingtonians think the joys of square dancing outweigh the wisecracks tossed their way. No one can say for sure exactly how many dancers there are because most diehard dancers (i.e. , all of them) belong to more than one club.

And interest appears to be growing, said Washington Area Square Dancers Cooperative Association president Bill Mitchell.

Washington, in fact, is a real square-dance heaven. At last count 171 clubs were registered with WASDCA. "There are five or six places to dance every night of the month," Mitchell said, with clubs for teens to senior citizens and ambiences ranging from relaxed, social gatherings to rip-snortin' hoedowns.

Square dancers are nothing if not enthusiastic, and to lure even more people into their ranks they're sponsoring National Square Dance Week next week, Monday through Saturday. If your last contact with square dancers was in your grade-school gym class, you can watch some real pros in action at one of the free demonstrations scheduled for next week at area shopping malls. And if you're inspired to try a couple of do-si-dos yourself, WACSDA and the local Callers Association are sponsoring a series of "first-nightrs" - free get-acquainted dances for beginners - throughout the area for the rest of the month.

Washington's not the only city with a hard-core square-dance population. If you doubt that the hobby is big business take a look at "American Squaredance," an Ohio-based monthly magazine with a circulation ow 45,000. A recent issue had ads for dresses, shoes and petticoats; even Petti-tainers ("the innovative and convenient way to store your petticoats"). You could order needlepoint kits, T-shirts, license plates, greeting cards, address labels, bumper stickers ("I'd Rather Be Dancing"), dancing dude-ranch vacations, banners, throw pillows, cookie cutters and mail boxes. Not to mention a weathervane with a dancing couple on top instead of a rooster ("Tastefully adorn your home and at the same time identify yourselves to all as SQUARE DANCERS.").

Closer to home, there's "Calls'n'Cues," WASDCA's monthly magazine, a good local source for classes, club news, 100-yard petticoats and other necessities of square dance life.

It's tempting to dismiss square dancers as suburdan-style hicks caught in a time warP. But ask them why they do it and they'll patiently go down the list for you: it's fun, it's good exercise, it's cheap, you meet so many nice people . . .

In the end it always come down to the old-fashioned virtues. The people who sqaure dance feel strongly about the importance of the family and find the hobby one of the few activities in this splintered society that brings the family together.

Ask Johnson. A technical administrator with the Department of the Army, he belongs to three square-dance clubs and hits the dance floor at least twice a week. Three years ago that was the last place you'd find him.

It was his wife's idea, he said. "She wanted to get me away from the TV. I said, 'Square dancing? You gotta be kidding!'

"But I found that square dancing kind of brings the mother and father back together," he said. "More often than not, the husband goes bowling and the wife goes to her sewing circle or garden club. There aren't too many activities they can do together. Square dancing is ideal.

"Now I wonder where in the world I'd been all those years."

It's easy to sneer, but the fact remains that square dancing isn't as easy as it looks. One over-enthusiastic beginner, carried away after mastering the basic steps (do-si-do, allemande left, promenade), kept having to be told to stop bouncing around. Despite the twangy music, square dancing is not bouncy, and there's no rompin' and stompin'. It's made up of graceful, gliding movements. That's why the ladies wear those soft flat leather shoes, so they can shuffle better.

There's a reason for those outlandish skirts, too. They add to the flourish of the dancing. A good dancer knows how to swirl them for maximum impact, and a woman in slack finds a definite lack of finesse in her dancing.

It's exhilarating to be whirled around from partner to partner and there's mental challenge. The dancer strains to hear the calls (like trying to understand an auctioneer) and, once they register, battles to remembers (a) right from left (b) how to do the step. By that time everyone else is two steps ahead. It's part of the fun.