Well, first you need to figure out why they don't want you to play the drums... in order to know what you need to do to get them to allow you to play the drums.
Are they concerned about all of the noise that will come from the drums if you were to get them? Maybe you and your parents could make a compromise. Such as times you can play, how long you can play, where you can play, etc... Do you have a basement, or garage? Perhaps they would allow you to play the drums in there.
Are they concerned about the money that they would have to spend on the drums, and accessories? Maybe you and your parents could make a deal. If you earn enough money to buy the drums and accessories yourself, then you can buy them. You can either earn the money from doing chores around the house, getting a job, or doing side jobs. Check out my How To, it may help in money - http://www.funadvice.com/howto/money_16
The only thing i can add to this is soundproofing but that's almost always expensive. However, a couple of old matresses against the adjoining wall where your parents are would absorb some of the bass frequencies which would help a bit. I was all set to give a nice big long informative answer here but Angelee beat me to it! Ha good luck.
dont give them an option say you're playing them weather they like it or not.