On July 17, 1998, at 0800 central daylight time, a Piper PA-25-235, N75HM, piloted by a commercial pilot, received substantial damage on impact with terrain during landing on runway 25 (2500' x 100', turf) at Leland Field near Leland, Illinois. The aircraft bounced and made a hard landing. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 agricultural instructional flight was not operating on a flight plan. The student reported minor injuries. The local flight departed Leland Field at 0750. In a written statement, the student reported that he had enrolled in the instructor's agricultural pilot training program. The commercial rated student stated that his total flight time was 300 hours, three hours of which were in the accident airplane. The student did not possess a tail wheel endorsement. The lesson plan was to practice takeoff and landings. The student was told to release the control stick when it was yanked upon by the instructor. During the student's third landing, the aircraft bounced, the instructor yanked the control stick and reentered the traffic pattern, at which time he released the controls to the student. During the student's fourth landing, the aircraft bounced, the instructor yanked the control stick and the student released the controls. It was also stated by the student that when the instructor took the control stick, the instructor said, give me the stick, and applied full power. The student observed the airspeed to be 50 KIAS. The airplane continued 2/3 down the runway a little nose high. The nose then pitched upwards and the airplane stalled. The right wing dropped and the nose impacted the ground. The instructor reported that the student bounced the landing and applied full aft control. The instructor called out, "my controls", but the stick remained in the full aft position. The instructor attempted to fly the aircraft with throttle and rudder. Inspection of the elevator control system by a Federal Aviation Administration inspector found no anomalies. A functional check showed full up and down travel of the elevator system.