During an instructional flight, the student pilot and flight instructor planned to stay in the traffic pattern for touch and go landing practice. During the third approach, just prior to the landing flare, the airplane began to drift to the right side of the runway. The flight instructor noticed that the student was cross controlling with the nose of the airplane point towards the right. He took over the controls and initiated a go-around. The flight instructor stated that the student pilot did not immediately remove his feet from the rudder pedals, which made his control inputs "less effective." While still airborne, the airplane struck a runway sign. The flight instructor continued the go-around and landed without further incident. He reported that the flight controls were "free and correct" and did not report any preimpact mechanical malfunctions with the airplane. Examination of the airplane by a Federal Aviation Administration inspector revealed substantial damage to the right wing.