Lark does make a good point, we need to be wise, while you shouldn't hide away, you should know the time and place for these things. i told my mom first because i was close with her and i'd feel terrible lying. it wasn't until i met another pagan that i told others. we were in a group and she introduced herself as one [because she saw my necklace] and i said i was too. that's how my friends found out, and it turns out a couple of them were Pagan also, they just didn't want to speak up. i'm now an adult, if someone asks me directly, i'll tell them, otherwise i just go about my business. my last employer asked one day because i'd work Sundays and certain holidays the store was open, but take off other days like Halloween or the Solstice, so I told him. he was fine with it, asked me a lot of questions out of interest. i'm odd, i love religious conversations, as long as they don't turn into a 'mines better than yours' debate. so i use my intuition, if i feel someone won't be too happy knowing i'm a Witch, then i change the subject or lie. otherwise i'll tell them, but i try not to dwell on it, it's really not important.
while not everyone's parents will be supportive [i know my dad lost it when it came out] you should sit them down and have a discussion about it. do not try and start a fight, if you notice things are getting to that point, say so you don't want a fight, so can we continue later. compile some information for them to read, perhaps a couple key points for yourself just in case you get nervous. you should also try to see things from their perspective, understand why they're upset, then calmly explain your standpoint to them. it might not get you accepted, but if you explain yourself it couldn't hurt. i read in a book [The Goddess is in the Details by Deborah Blake] as pagans we live with different types of people [can't remember all of them atm so i might forget one] there's those who have nothing wrong with your religion, those who say it' fine, but hope you'll convert, those who clearly aren't happy with your choice and constantly berate you, those who avoid the issue, and those who outright hate you and demand you change. i've dealt with all but the last one, the first two and the second last one are the best, because you don't really have a lot of problem with them. you need to figure out if they're happy or not, because you don't want to upset someone who clearly isn't happy with your choices by putting up a pentagram in the living room. the people who berate you are the worst, they'll put you down and when you ask them to stop they're say they're not doing anything. it can take a lot out of you.
if your parents aren't happy with your choices, even after sitting down and discussing them, inform your parents 'this is who i am. i know you're not happy, i understand, so i won't leave my Wiccan stuff out, but i'm still Wiccan.' and leave it at that. don't bring things up about your faith and let sleeping dogs lie. [as it were] one day you will move out, on that day, you can have a bookshelf full of your Wiccan Books, hang a pentagram on the wall, leave out your athame and do whatever. for the time being though, your parents house, so lay low and avoid conflict.