Little Savion Glover used to sit in the back of a Broadway Dance Center (221 West 57th Street; 582-9304) studio and do his homework. Now he's got Broadway under his belt and Hollywood calling. It's enough of a fairy tale to make a kid fork over 25 bucks for a packed master class with the legend of ease: Glover periodically teaches at his old studio, where ongoing tap classes cover the old hoofing days of Buster Brown, the rhythm and Broadway styles, and the unique hard-hitting technique of Savion and his crew. Fifty classes are taught by legends like Frank Hatchett (Glover's teacher) and Fosse choreographer Chet Walker. If you're not waiting to be discovered, check out the "Absolute Beginner" tap workshops and keep in mind master Glover's advice: Keep that metronome going back and forth, listen hard, and don't forget to find the pause.