The flight instructor reported that during an instructional flight, she and her student pilot were practicing autorotations. During a right turn 180- degree autorotation, the flight instructor announced that the throttle was coming on, and then when full throttle was on. The student then started to level the helicopter. As the wind had shifted during the maneuver, the student was forced to flare harder and utilize increased cyclic control. The flight instructor subsequently took control of the helicopter in order to prevent an engine over-torque and landed the helicopter. During the landing, the tail boom was substantially damaged. The flight instructor reported no preimpact mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation.