On March 25, 2000, at 1155 central standard time, a Cessna 152, N6375H, operated by a certified flight instructor (CFI), nosed over during a forced landing in a field, southeast of Butler, Missouri. The CFI and student pilot on board were not injured. The airplane was substantially damaged. The 14 CFR Part 91 instructional flight was operating in visual meteorological conditions. No flight plan was filed. The flight originated at Clinton, Missouri, at 1110 cst. The CFI reported they were practicing a simulated loss of engine power when the accident occurred. He reported that instead of pulling the power to idle, he pulled the mixture to idle cut off to "...demonstrate a lesson to the student should he inadvertently pull the mixture instead of the throttle." The CFI reported that he emphasized to the student that he needed to maintain a higher than normal glide airspeed to keep the propeller windmilling. He reported that they chose a field and during the turn onto final approach at an altitude of 2,500 feet mean sea level, the propeller stopped windmilling. The CFI reported he took control of the airplane and attempted to get the engine started to no avail. A forced landing was made in an open field. He reported that the field was rougher than anticipated. The nose gear collapsed during the landing roll and the airplane nosed over.