The helicopter was being used for flight training. The student had been experiencing some problems in stabilising the hover so the instructor placed the helicopter light on the skids to allow the student to practice use of the cyclic control. Because the student had a tendency to allow the helicopter to drift right as the helicopter came light on the skids, the instructor gave the student control of the cyclic and yaw pedals whilst he retained control of the collective. After several attempts, the student's cyclic control had apparently improved sufficiently that the instructor was confident to bring the helicopter into the hover. However, during the following three attempts the student found hover control difficult and after several seconds in the hover, the instructor had to take control. During the fourth attempt, the student allowed the helicopter to drift right slightly. With the helicopter approximately 1 ft off the ground, the student unexpectedly made a large right cyclic input and allowed the helicopter to yaw left. The instructor did not respond quickly enough to prevent the helicopter sinking and the right rear skid struck the ground. As the ground contact was firmer than normal, the instructor decided to air taxi the helicopter to the parking area. The helicopter's airframe, right skid and tailboom were found damaged.