AFTER BACKING OUT OF PARKING SPACE WITH SHIFT LEVER IN DRIVE POSITION, THE ENGINE OPENED UP AT FULL THROTTLE WITHOUT FOOT APPLIED ON ACCELERATOR PEDAL. VEHICLE WAS THROWN OFF ROADWAY, CRASHING INTO A SCHOOL BUILDING. ALL 5 OCCUPANTS WERE HOSPITALIZED WITH SERIOUS INJURIES. INSPECTION REVEALED THAT THE THROTTLE VALVE WAS IN FULL OPEN POSITION. *TT *NLM