Plan A: Agree with everything they say, tell them what they want to hear, afterwards just carry on with your life exactly the same. They won't realise you haven't changed until the PO comes around again next year, repeat the performance again and by the time the PO comes around again you should be about outta there!
Plan B : On the other hand...if you have very pushy parents...try telling them that you 'want to make the truth your own' and any pressure from them upsets you. Tell them that you want to think about things for a while and make up your own mind about 'the truth'. They may ask if you have any 'doubts'. Don't be specific, just say that you need time. Imply that pressure to conform might make things worse..maybe they'll be happier with a wavering child rather than a rabid apostate!
You know, thinking about this there ain't no easy answer! Just remember that hundreds if not thousands of JW young-uns are going through exactly the same situation around the world.
My sympathies.