The flight instructor stated that on the eighth traffic pattern approach, the student pilot maintained a stabilized approach on the centerline and on short final. At 50 ft above the ground, the flight instructor told the student pilot to reduce engine power. Then, he instructed the student to “flare now,” but the student continued the approach in a nose down attitude. As the flight instructor began to take control of the airplane, it impacted the runway “hard” with the main landing gear and bounced. The flight instructor added power in an attempted go around maneuver, however, the airplane “began to stall.” The airplane descended, the right wing struck the runway marker, the nose struck the ground, and resulted in the airplane coming to rest inverted. The rudder and fuselage were substantially damaged during the accident sequence. The flight instructor reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.