I wanted to tell them but I got caught before that at 16. Youll probably get caught at some point even a stealth master like myself couldnt keep it up.

Just pick a really good time to come out about it, preferably after getting some great grades at school. That way they cant say "look what its doing to you, youre grades are going down; youre unfit etc..". Theyll look for problems in your life to blame on it so dont give them any. If they see youre doing well while smoking pot it may drastically change their views.