If your parents would actually call the cops on you for smoking pot, then they don't deserve the pleasure of having you as their child. I'd say move out, but since you're 15 you can't really just do that. I'd suggest that you hide it from them, it gets easier if you get your own car, until you can move on and start your own life. If your parents are too ignorant and stubborn to understand and accept your lifestyle then you are under no moral obligation to accept theirs. I moved out when I was 17 for the same reason and didn't speak with my parents for a full year, but since they realize they messed up and have apologized to me countless times and are trying to repair our relationship.