Still, some committed online educators remain unconvinced. Tim Snyder, the executive director of Colorado Online Learning, which offers more than 50 online courses to Colorado schools, included physical education with studio art, marching band and the laboratory sciences as subjects best left to brick-and-mortar schools. "These are still better experienced in a hands-on setting," Dr. Snyder said. But online gym has prospered. That has been possible in part because physical education itself has evolved. Once a highly regimented class centered on team sports and competition, physical education now emphasizes healthy living and personal fitness, topics some see as eminently suited for independent Internet study.