On September 13, 1994, at 1600 central daylight time, a Cessna 172RG, N616SF, registered to Planemaster Services, Inc. of West Chicago, Illinois, and operated by a commercial flight instructor and a commercial student, departed controlled flight on short final to a landing on runway 15 (3,401' X 100' dry/asphalt) at DuPage Airport, West Chicago, Illinois, and impacted on the runway. The airplane sustained substantial damage. The instructor pilot and student reported no injuries. The local 14 CFR Part 91 instructional flight was being conducted in visual meteorological conditions. No flight plan was on file. The flight departed West Chicago, Illinois, at 1515. The student said that he was making a power off approach in accordance with the flight instructor's instructions. He stated as he came closer to touchdown he asked the instructor if he could add power, but did not receive an answer. He stated that he then "pushed the throttle forward and pitched up." He said at that point the instructor said, "Don't stall." But the airplane sank "too fast for me to react." The instructor stated that he was giving the student instruction in a "precision approach." He stated that when the student thought they were too high, "... he cut the power increasing the descent rate. He flared abruptly at approximately 20 feet above runway putting aircraft in a stall. He added power at this point, but it was too late... ."