Tips on dating in secret?

So my parents are the biggest idiots to ever live. (for more info go to my other question, http://answers.yahoo.com/question/index;_ylt=AtbkBkupS.wEdWMageC8xwPsy6IX;_ylv=3?qid=20110701173048AAmMPLF ). They won't let me date even though I'm 15. However, there was this guy who's been my friend for 6 years. Yesterday he asked me to be his girlfriend. I want to say yes (and if fact I did), but my parents hate him and want me to have nothing to do with him. Ay advice on how to play it?