On October 5, 2017, about 1420 Pacific daylight time, a Piper PA-24-250, airplane, N7892P, was substantially damaged when it was involved in an accident at Hillsboro, Oregon. The flight instructor and student pilot were seriously injured. The airplane was operated by Twin Oaks Airpark Inc. as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that, during a practice soft field full stop landing, as the student pilot was approaching the runway, the airplane descended quicker than expected. As the airplane got closer to the runway, the airspeed was decreasing, the nose angle was increasing and he called out to the student "airspeed." A go-around was called and during the go-around, the airplane aerodynamically stalled, and settled towards the runway. The airplane struck short of the runway hard, and then bounced onto the runway. According to the student pilot the soft field landing had a shallower glide path than a normal landing. He stated that while flying the approach, he noticed that the airspeed was about 15 knots slow. Subsequently, the flight instructor called for him to go-around. During the go-around, the flight instructor told him to apply the power quicker. As the airplane approached the flare, he felt the airplane settle towards the ground in an aerodynamic stall. Furthermore, he stated that he noticed no wind (crosswind or downdraft) on final. Both wings and the fuselage were substantially damaged. The pilot reported no preaccident mechanical failure or malfunction with the airplane that would have precluded normal operation.