THE STUDENT HELICOPTER PILOT WAS CONDUCTING A LOCAL AREA SOLO FLIGHT. AFTER PRACTICING SEVERAL TAKEOFFS AND APPROACHES THE STUDENT PILOT RETURNED TO THE DEPARTURE AIRPORT AND EXECUTED AN APPROACH TO A HOVER AT THE OPERATOR'S FACILITY. THE STUDENT PILOT THEN AERIAL TAXIED TO THE DESIGNATED PARKING AREA. WHILE MANEUVERING REARWARD TO LAND IN THE SPOT, THE HEEL OF THE SKIDS STRUCK THE GROUND AND THE HELICOPTER TIPPED BACKWARD STRIKING THE TAIL ROTOR BLADES ON THE GROUND.