On December 8, 2011, at 1645 central standard time, an experimental amateur-built Shook Rans S-12 airplane, N7138K, was substantially damaged when it collided with trees near Festus, Missouri. The flight instructor and student pilot were not injured. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed for the instructional flight, which was operated without a flight plan. The local flight originated from Festus Memorial Airport (KFES), Festus, Missouri, at 1615. The student pilot had recently purchased the airplane and was receiving flight instruction toward a sport-pilot license. Neither the student pilot nor his instructor had flown the airplane before the accident flight. The purpose of the flight was to practice takeoffs and landings. The flight instructor reported that the airplane was too high on final approach in order to land on the first third of the runway and that he told the student pilot to perform a go-around while the airplane was about 50 feet above the runway. Shortly afterward, the student pilot applied maximum engine power and the airplane entered a steep left climbing turn. The student pilot over corrected and the airplane subsequently entered a steep right turn. The flight instructor reported that the airplane was in an incipient aerodynamic stall/spin when he assumed control of the airplane. The airplane collided with trees during the subsequent stall/spin recovery, resulting in substantial damage to both of the wings, tailboom, and empennage. The flight instructor stated that there were no preimpact mechanical malfunctions or failures that would have precluded normal operation of the airplane. Additionally, he noted that the accident could have been prevented had he assumed direct control of the airplane sooner instead of providing verbal corrective actions to the student pilot. The nearest aviation weather observation station with recorded historical weather information was at St. Louis Downtown Airport (KCPS), about 29 miles north-northeast of the accident site, which was equipped with an automated surface observing system (ASOS). At 1653, the KCPS ASOS reported the following weather conditions: calm wind; visibility 10 miles; sky clear; temperature 4 degrees Celsius; dew point -4 degrees Celsius; altimeter setting 30.19 inches of mercury.