Though the lavish format and first-person artifice are the same, it's easier to warm up to ten-year-old Torrance York than to the riding and dancing princesses of Krementz' earlier productions. Her matter-of-fact attention to business comes through straight off, as she reels off regulation times, distances, events, and levels of competition; and she is seen mostly at practice, sometimes in competition, always concentrating on the routines themselves. ""It's not the individual tricks that are hard, but putting them together,"" says Torrance, whose conversation runs to statements like ""and for my dismount I did a tucked gainer off the side."" Highlights of Torrance's year are a trip to Germany to compete against girls' school teams there, an all-around first place in the New York City Interschool Championship where her school got the trophy, and the thrill of seeing Nadia and others at the Garden. In between there are after-school and evening practice, morning ballet lessons, competitions on Fridays, and gym camp in summer. Yes, Torrance sometimes thinks about the Olympics, but ""right now what I really want is to get my back layout on the beam and make it stick."" If you couldn't help speculating on the cost of maintaining A Very Young Rider, here it's the hard work, long hours, and enthusiasm that impress. Glossy, but personable.