THE PILOT INADVERTENTLY TURNED OFF THE MAGNETO SWITCH DURING A GO-AROUND, RESULTING IN A LOSS OF POWER. ALSO CAUSAL TO THE ACCIDENT WAS THE FAILURE OF THE PILOT OF A SECOND AIRPLANE TO RESPOND TO THE TOWER CONTROLLER'S INSTRUCTIONS. A FACTOR RELATED TO THE ACCIDENT WAS THE PILOT'S LIMITED FLIGHT EXPERIENCE IN THIS MODEL AIRPLANE.