the same as high school, 4kg or 8.8 lbs
The sport is called the "Shot Put". The shot is 'put' as far from the contestant as possible. So the question is, "How heavy is the shot in the 'shot put event' for boys aged 15?" The answer is 12 pounds.
Shot put is to try to throw a heavy ball the longest distance
I would describe the shot put as a round and slightly heavy metal or hard plastic ball.