Following a dual check, the student was briefed to carry out a series of circuits and landings. During the first of these the aircraft microphone failed, and a full stop landing was made in order to obtain a replacement. A normal takeoff and circuit was then flown, however the aircraft was low on approach and the pilot elected to carry out a go-around. After reaching a height of about 200 feet the aircraft was placed in level flight. A descent was then commenced, followed by a turn through 270 degrees. At this point the aircraft touched down in a paddock, became airborne again, then collided with a roadside sign and a power line. It then struck the median strip of a main road and came to rest after colliding with the aerodrome boundary fence. Initial investigation revealed no fault or malfunction of the aircraft which might have contributed to the accident. The student was making his sixth solo flight and had accumulated less than 2 hours in command. No fault was found with the aircraft which might have contributed to the accident. The pilot had experienced considerable learning difficulty during his training as indicated by his having flown only two hours solo in a total of 50 flight hours.