On February 9, 2005, at 1645 central standard time, a Piper PA-18-150, N66ND, nosed over following a collision with a snow bank while landing on runway 12 (2,600 feet by 50 feet, dry asphalt) at the Larimore Municipal Airport (21L), Larimore, North Dakota. The certified flight instructor (CFI) and the private-rated student pilot were not injured. The airplane was substantially damaged. The 14 CFR Part 91 instructional flight was operating in visual meteorological conditions without a flight plan. The flight originated from Grand Forks (GFK), North Dakota, on 1600. The CFI reported the purpose of the flight was to provide tailwheel training to a private pilot who was taking a tailwheel transition course from the University of North Dakota. The CFI stated they departed GFK and flew to 21L to practice landings. He stated the student made the first landing. The CFI stated he then demonstrated a wheel landing. The student made two more landings with little assistance. The accident occurred on the student's fourth landing of the flight. The CFI stated the student landed on the main gear and after the tailwheel came down the airplane "turned slightly left of centerline." He stated the student overcorrected and the airplane veered abruptly to the right. The CFI stated he applied full left rudder, but it was too late. The airplane ground looped, struck a snow bank on side of the runway, and nosed over.