Okay, so will need more information. Exactly how are your parents preventing you? I am a mom and I think most parents out there expects/support teenagers working; in your case starting a small business.
This leaves me to speculate that they are concerned about you taking money from other people/kids for a product that they are not certain about. If that is the situation, which I do understand; you will have to demonstrate to them that you have the knowledge and skill to do this on a professional level. As you are under 18, if something goes wrong, or someone has complaints, the responsibility falls onto your parent(s).
Give me some more information and I'll see what advise I can give you.
Also lookup Pia Bows and pm her, she does an amaizing job and she also started young.....