The flight instructor and student pilot were practicing landings in a tailwheel-equipped airplane. The flight instructor stated that on the fifth landing, during the landing roll, the airplane began to drift slightly to the right, and the student pilot inadvertently applied right rudder. In an effort to correct for the right turn, the flight instructor immediately applied full left rudder and brake while simultaneously pulling aft on the control yoke, but the airplane ground looped. During the ground loop the airplane sustained substantial damage to the left wing and left aileron.