The student pilot and certified flight instructor (CFI) were practicing touch-and-go takeoffs and landings. While on the downwind leg in the traffic pattern, the CFI retarded the throttle to simulate an emergency. The student pilot continued the approach and initiated a forward slip to correct for an altitude deviation. He continued the slip until 25 feet above ground level, at which time he added power and initiated a go-around. The airplane started to roll to the left and, at 20 degrees, the CFI took control of the airplane. The CFI attempted to counter the roll, but the airplane was unresponsive, and he decided to land. The airplane impacted in a left-wing-low attitude. The empennage separated from the fuselage, and all four engine mounts were broken. The operator reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.