Try being open with them. Get them involved. Actually show them that what you are doing is fine. Also let them know you are very passionate about your practice. Start acting responsible and tell them you wil be careful and safe with what you are doing. After they accept it dont bring it up further. You run the risk of annoying them.
I had a similar experience and for five years i learned the craft in shadow. You know the phrase, "Book of Shadows" is a term gathered because in the elder days when witches were burned they had to practice and in secret, hence shadows, so that they were not discovered. So therefor you may have to go in the shadows to practice and learn at your own pace. Hide things, if your worried about it being discovered. Bless your hiding place so the unwanted eye or mind wont think to look there.
It is always difficult with parents who still have control of their children. Best to obey your parents, and keep your beliefs secret!
You don't need tools to practise witchcraft; you can practise just by meditation.
I agree with Bry. I feel that you should respect your parents, so long as you live in their house and they afford you the lifestyle you live. You can study it on your own and continue to learn and grow, but until they are either comfortable with it or you move out, respect is key.