Is it the growing or the space usage which your parents are opposed to? I only ask because it's bound to get a little smelly in there as they grow and so you may need to find a way to deal with that odour at some point without a carbon filter, however if it's space then as long as you're maintaining a smell-less area around the outside of your home and not keeping bad company you should be fine.
I'm obviously not going to judge you for having a secret plant which your parents can't know about, but just remember how smelly it'll get.
So does patronising and insulting someone like this =P. If you want to grow weed, it's your choice, just keep it hidden if it's a permission problem.