THOUGH A classic art form, ballet is a relative youngster on American soil. In fact, the oldest American ballet company, the San Francisco Ballet, marks its 70th year just this season. Other American companies of renown -- including the New York City Ballet and American Ballet Theater -- are younger. To find a former dancer who experienced the critically acclaimed San Francisco Ballet's youth, one doesn't have to search further than the company's 325-student school.

There, Jocelyn Vollmar, 77, one of San Francisco Ballet's first generation of dancers, teaches a daily pointe class to advanced ballet students. "I joined the school at 12 years old," she said one morning before setting off to teach her 14- to 18-year-old charges. "Then it was called the San Francisco Opera Ballet."

"Our legacy is quite wonderful," Vollmar says. "There were very few ballet schools in America at the time. We all lived at home and we were just kids who would go take ballet after school. In those days there was no pressure," she says, because no professional ballet companies existed to compete against.

William Christensen became artistic director the same year Vollmar began her studies. "He insisted that we have a company," she says, "so we danced in skating rinks, parking lots, on splintery stages. . . . There was no money at all, and there was no place else to go [in the United States] if you wanted to dance." Expertly trained by Christensen and his brothers, dancers Lew and Harold, in 1940 the fledgling company staged the first full-length "Swan Lake" in the United States. Vollmar was among the corps de ballet. Four years later in a threadbare tutu that Vollmar says she and her mother sewed, the company launched a national holiday tradition with the American premiere of the first full-length production of "The Nutcracker." Vollmar stepped out of the corps to dance the role of the Snow Queen.

Ballet has taken Vollmar around the world: Her performing career spanned 30 years, 16 as a ballerina with the San Francisco Ballet. She joined the just-founded New York City Ballet as a principal dancer in 1948 and stayed for two years before leaving for Paris and a decade touring Europe, Australia, Scandinavia and North Africa. In 1956 Vollmar returned to San Francisco for good and attained the rank of prima ballerina; she retired from the stage in 1972.

"San Francisco Ballet has always been my home, my family," Vollmar says. "We literally built it from scratch and over the years we've attracted wonderful choreographers and dancers and our alumni dance all over the world." Of the contemporary repertory, which the company brings to the Kennedy Center Tuesday, the former prima ballerina says, "The basics of ballet are always there, they never change. What changes is that choreographers are developing it in new ways that open our eyes to all the wonders of the world around us. It's very good for us as dancers and for choreographers to stretch their creative muscle."

Two Balanchine ballets, "Serenade" and "Ballo della Regina," and Jerome Robbins's exquisite plotless community in motion, "Dances at a Gathering," set to Chopin piano pieces, will be performed here. The company's newer works on the pair of repertory programs include Mark Morris's witty "Sandpaper Ballet" to the playful compositions of Leroy Anderson, and two works by current artistic director Helgi Tomasson: "Prism," an abstraction for 29 dancers to Beethoven's Piano Concerto No. 1, and "Chi-Lin," a blending of traditional Chinese mythology with American inventiveness that uses an East-meets-West score by composer Bright Sheng.

Vollmar, also a published poet, sees the longevity of a troupe like San Francisco as an endorsement of the importance of the arts: "Art is the exquisite joining of already existing things that long to belong together . . . During bad times the arts always flourish because the soul needs that artistic expression."

SAN FRANCISCO BALLET -- Nov. 26, 29, Dec. 1, "Ballo della Regina," "Dances at a Gathering," "Sandpaper Ballet"; Nov. 27, 30, "Serenade," "Chi-Lin," "Prism," Kennedy Center Opera House. 202-467-4600.

The San Franciso Ballet -- the oldest in America -- performing "Prism."