THE STUDENT PILOT HAD RECEIVED ABOUT THREE HOURS IN THIS MAKE AND MODEL OF AIRCRAFT. AFTER ABOUT 45 MINUTES OF DUAL INSTRUCTION, HE WAS INDORSED FOR SOLO FLIGHT, THE INSTRUCTOR DEPLANED, AND THE STUDENT TOOK OFF TO FLY LOCALLY. ABOUT 25 MINUTES LATER, THE STUDENT RETURNED FOR TOUCH-AND-GO LANDINGS. HE STATED THAT ON DOWNWIND, HE ELECTED TO CHANGE THE FUEL SELECTOR POSITION. HE SAID THAT HE REACHED DOWN, DEPRESSED THE SPRING CLIP, AND ROTATED THE FUEL SELECTOR HANDLE TO THE RIGHT. DURING THE GO-AROUND AFTER THE LANDING, THE ENGINE QUIT AT ABOUT 300 FT AGL. SUBSEQUENTLY, THE AIRCRAFT CRASHED DURING A FORCED LANDING IN AN AREA OF SCRUB PINE AND OAK. REPORTEDLY, THE PILOT HAD TURNED TO AVOID LARGER TREES DURING THE LANDING. THE FUEL SELECTOR WAS FOUND IN THE "OFF" POSITION (NEAR THE RIGHT TANK POSITION). ABOUT 15 GALLONS OF FUEL WAS REMAINING IN THE RIGHT FUEL TANK.