I'll offer a totally different opinion. You don't need to agree, and since I don't know any of you, I'm not sure that it's the right approach for you, but here's my 2Cents:

Tell your parents that you'll do what they say. If you continue to smoke, be more carefull, and don't get caught. Get to a point in your life where you can live independently from them (finish ur education, get a job, set up your life). Become an adult and establish your own life and rules.