As the last golden leaves of autumn float lightly to earth, scores of ballet schools across Canada get into full lilting swing. From split-level bungalows, apartment buildings, farmhouses and subdivisions, in cities and towns from Newfoundland to British Columbia, youngsters from thousands of Canadian families attend weekly ballet classes. Doting parents, looking on fondsly from the sidelines, watch hopefully for signs that their small daughter may be among the gifted few of Canada's 2,000,000 five to fourteen year-old girls who develop the poise and twinkling toes of a budding ballerina. For little girls themselves, ballet lessons are long hours spent trying to look as if they really were made of sugar and spice and all things nice. Exercising in leggy groups, wearing leotards or frilly ballerina skirts, posturing in front of full-length mirrors -- few little girls can resist the magic of the ballet class and its centuries-old enhancement of youthful grace.