When am i too heavy to do ballet?

-Im nearly 12 stone heavy and 14 years old, am i too old/ heavy to begin ballet? PLEASE HELP!!!I have no idea what 12 stone means, if you gave pounds or kilograms, I would have understood. I think that unless you are over 200 pounds and and in a pas de deux class, you aren't too heavy. The heaviest girl in this class is the best dancer in my opinion. http://www.youtube.com/watch?v=QGKxtUZUD鈥?/a>