The student held a private pilot certificate with a helicopter rating and was receiving instruction toward a commercial helicopter pilot certificate when the accident occurred. According to the instructor, the student pulled aft cyclic too early while beginning a landing flare following a practice autorotation. This resulted in an increase in main rotor rpm and a decrease in airspeed. The instructor then adjusted the throttle in an attempt to decrease the rpm. The instructor stated the student then applied excessive left pedal, which resulted in the helicopter making a 180 degree turn while the helicopter was six feet above the ground. The instructor stated he then decreased the collective and put the helicopter on the ground before the situation worsened. The helicopter contacted the ground as it skidded backwards resulting in substantial damage to the tail boom.