The flight instructor and student pilot, who was the owner of the airplane, were practicing simulated engine out/aborted takeoff procedures. The student pilot completed one aborted takeoff without incident; however, during a second attempt, he overrotated and the airplane climbed to an altitude of about 20 feet. The student pilot applied full engine power and landed on the runway; however, he did not reduce the engine power to idle when instructed. The instructor attempted to take control of the airplane, but the student pilot reported that he did not relinquish the flight controls to the instructor in a timely manner. With full power, the airplane tended to turn left, and the instructor applied right rudder and brakes, but was unable to overcome the full power setting, which the student still had not reduced as instructed. The airplane departed the left side of the runway and struck a runway sign, which resulted in substantial damage to the right wing. The pilots reported no preimpact mechanical malfunctions with the airplane that would have precluded normal operation.