Religiousness doesn't mean you are intolerant first of all. Secondly...you don't have to change your faith to believe in magic. Your faith is your faith, you choose to change it. There are no restrictions beyond those you allow or you believe in. You determine your faith, not anyone else.
That being said, you can A. choose to hide your practice, or B. choose not to hide it. Most people hide it. I am of the opinion that we should never have to hide for your beliefs. But in the end it is your decision on what you do. Remember, once you officially become an adult (18 in the US) you can move out, get a job, and a place to stay, and then your parents can't prevent you from practicing.
That being said, for the time being stick to direct energy workings, or workings that don't require a lot of interesting materials. For instance, a sigil is a drawing...
...these are some of my sigils. You can always say "Mom, they are just doodles." And no, you don't necessarily need the circle around them, so the doodle story may very well hold up.
You can also do other things that won't be suspicious. Lol. It is all on you and what you are comfortable with. See how they would feel about it first. Bring up what you wish to follow in conversation and ask what your parents think of that. ;)