The flight instructor was conducting the 16-year-old student pilot’s first instructional flight. After completing several takeoffs and landings, they “taxied around the airport multiple times,” during which they experienced “light to sometimes moderate” rain. At the conclusion of the lesson, the rain became heavy enough that visibility was reduced, and the instructor decided to taxi the airplane into its open hangar to avoid getting wet. As they approached the hangar, the instructor noted a set of wheel chocks on the ground, and with the engine still running, he instructed the student to exit the airplane, walk around the propeller arc, and move the chocks so that he, “could taxi the airplane nose-first into the hangar…then turn it around once inside and shut down.” He stated that he repeated the instructions to ensure that the student understood. The student subsequently exited the airplane and walked forward into the spinning propeller, resulting in serious injury. The instructor reported that there were no preaccident mechanical malfunctions or failures of the airplane that would have precluded normal operation.