On October 20, 1994, at 1500 Pacific daylight time, a Piper PA- 28-181, N8760F, operated by the California International School of Aviation, collided with rough terrain adjacent to the Rialto Municipal (uncontrolled) Airport, Rialto, California. Visual meteorological conditions prevailed at the time of the instructional flight. The airplane was substantially damaged, and none of the four occupants were injured. The crew consisted of a flight instructor (CFI), who held a commercial pilot certificate, and a student pilot. The flight originated from Pomona, California, at 1350. The CFI reported that during the accident flight he was, in part, attempting to teach his presolo student how to land the airplane. When the accident occurred, the CFI was specifically trying to instruct the student in performing a forward slip to a landing. According to the CFI, his student initiated the slip as he had instructed, and the airplane descended. During the approach, the CFI applied corrections to the amount of pitch his student was using, and at times he also made corrections to the flight path. The student initiated the landing flare by pulling the yoke up "fast and a little high," and the airplane started drifting left. The CFI also reported that, between 3 and 5 seconds before touchdown, he took the controls from his student and initiated corrective action; however, the airplane touched down hard several feet left of the runway centerline, and he lost control of it. The airplane veered off the runway and came to rest on a northeasterly heading in a field of weeds. Neither the CFI nor the student reported having experienced any mechanical malfunctions with the airplane. Runway 06/24 at Rialto airport was 4,500 feet long and 100 feet wide.