"When I first entered the High School for the Performing Arts," says William Scott, for seven years a principal dancer with the Dance Theatre of Harlem, "I'd had no training whatsoever, and no exposure to dance of any kind -- ballet, modern, jazz or whatever. They asked me to choose which I wanted to study, classical ballet or modern. Since I didn't know the difference, I picked modern."

Such were the modest beginnings of a career which was to burgeon into professional dancing with such troopes as the Chicago Ballet, Pearl Bailey's company and Dance Theatre of Harlem, the winning of two choreography fellowships from the National Endowment for the Arts, becoming a ballet master for Arthur Mitchell at the age of 21 and numerous other notable achievements.

Scott is now in Washington, winding up a six-week contract as assistant artistic director of the Capitol Ballet. He was called in from New York at the start of the year by founder-director Doris Jones to help whip the troupe back into shape after the departure of his predecessor, Keith Lee, and to prepare the program the company presents for a second time tonight at Montgomery Blair High School in Silver Spring. Among other items slated to be performed is Scott's own "When All Else Fails," to music by Aretha Franklin. Next fall, Scott will return to the District on a 40-week contract, to start building a secure and progressive future for the company.

Scott's own story is one of those bookstrap sagas that never fail to amaze -- a story of successful self-propulsion by an eager young man from an urban black family of scant means.Born in New York, he was attending a regular academic high school when he saw a bulletin calling for youths to participate in a variety show. He made up his own dance numbers for the show, and afterwards, spotting his talent, a gym instructor advised him to transfer to the High School for the Performing Arts. He worked in a car wash that summer to earn the money he'd need for tights, shoes and other gear.

"At first, I hated the place," Scott recalls. "I had no muscles or anything, and I was sore all the time. Besides, I was the only guy in a class of 25 girls -- it was really rough." By the end of a year, though, he was being singled out for performances and even teaching assignments. Among his own teachers were David Wood, of the Martha Graham company, and Gertrude Schurr, notorious among New York dance pedagogues for her strictness. "Her classes were murder," Scott says. "She kept telling me, 'If you don't learn to point your foot you'll never be a dancer,' and that made me more determined than ever." Schurr sent him for additional study to the Richard Thomas-Barbara Fallis school, where he was awarded a scholarship. During summers he also studied, again on scholarship, at the Graham school and the Harkness Ballett. At his graduation from Performing Arts, much to his own astonishment, he was presented with the coveted Helen Tamiris Award, and the entire graduating class flipped their caps in the air in his honor.

"After graduation," he says. "I took a job.I felt that's what you do -- you graduate, you get a job. So I got a job as a secretary. But after six weeks or so, something inside started whispering, hey, you have to dance.The boss pleaded with me to say, promised me raises and promotions, but I knew I had to go."

Scott danced for a while with Stuart Hodes' Ballet Teams troupe, when he heard that Arthur Mitchell was forming a school and company for the advancement of blacks in classical ballet. This was Scott's next step, and it proved decisive. He has all sorts of plans for his return to the Capitol Ballet in the fall, including expanding the repertory, enlarging the season, building audiences and, eventually, a touring program. He may even get back to dancing himself, which he's been away from for a year. For personal kicks, he says, "being on stage still does it the most."