According to the certificated flight instructor (CFI), the student pilot was conducting a practice straight-in autorotation with a planned power recovery from an altitude of 1,000 feet. The CFI stated that the helicopter’s rotor rpm was maintained throughout the maneuver. The student pilot initiated the flare during the recovery stage of the maneuver, but did not apply throttle, and the CFI did not react in time to add power in order to recover. The CFI subsequently took the controls and the helicopter landed hard. The main rotor contacted the tail boom, resulting in substantial damage to the tail boom, tail rotor drive shaft, and tail rotor control rod. The CFI stated that there were no mechanical malfunctions or anomalies with the helicopter.