The noninstructor-rated pilot reported that he agreed to go flying with a student pilot in the student's airplane and act as pilot-in-command while seated in the right seat. During the approach to land with the student on the controls, the airplane was high, but with the "airfield made," the student selected full flaps. According to the pilot, the airplane "got slow and low," and the student initiated a go-around, during which, in a single motion, the pilot raised the flaps to the full-up position, and the airplane "struggled to fly and climb." Subsequently, the airplane impacted trees at the end of the runway and came to rest on its right side. The pilot added that the Pilot's Operating Handbook states that the flaps should be retracted one notch at a time. The airplane sustained substantial damage to both wings, the fuselage, and the empennage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.