The flight instructor reported that she and the pilot receiving instruction were practicing autorotations. During an autorotation involving a right 180-degree turn, the flight instructor announced that the throttle was coming on, and then announced when full throttle was on. The pilot then started to level the helicopter. Because the wind had shifted to a tailwind during the maneuver, the pilot was forced to flare harder and use more cyclic control than expected. The flight instructor realized that completing a power recovery from the autorotation was going to result in an overtorque condition, took over control, and landed the helicopter. During the landing, the tailboom was substantially damaged. The flight instructor reported no preimpact mechanical malfunctions or failures with the airframe or engine that would have precluded normal operation.