How can I be famous whithout my parents knowing?

I think you have missed the meaning of the word 'famous'. Just because you can sing and dance doesn't mean you will hit it big. I suggest you pick another career so you can support yourself while you strive for your dream of making it big. If you do happen to make it in Hollywood....your parents will know about it. Trust me on this.

Becoming a internet star is one way. Joining a local dance/acting/singing studios can help you network. If you have drama teachers at your school ask them for help too. You can also interview with local and international talent agencies. But make no mistake. Becoming famous is not as easy as you think. You can have all the talent in the world and still never get noticed. If you're younger than 18 you will probably need your parent's help. Before you set out on that road I would advise you to really think about why you want to be famous, what you are willing to give up for it, and will it be worth it in the end. If you have a netflix account go and watch this documentary called The Hollywood Complex, it's all about preteens and teens trying to break into Hollywood. It's really interesting and insightful.

whatever path you take in life, good luck.

Look for independent movie casting or start by youtube. You're probably still a teen, I wanted to be internationally famous when I was a kid and believe me I was so close to this "world" I could touch it. It has a dark side. Know yourself really well before jumping in this because it ain't what it seems. It really isn't. Once you're in it's forever. Once you signed the paper, they own you! You can't un-famous yourself. Remember this. I'm glad every day that I haven't sign it. Know what it implies. Be on an independent label if you want it that bad. Never sign for a huge one. The music and movie industry is corrupted. Research what you're getting into.