The best way to convince someone is to be as informed as possible. Read, read and read some more. Know everything there is to know about husbandry and such, and then try to convince your parents that you know what you are doing. And if they still don't let you, just wait a few years, I remember my parents wouldnt let me get a snake, not because they were afraid, just because they thought I wasn't responsible enough, but a few years went by and I eventually convinced them that I was able to take care of a snake. Now I have 3 snakes, 2 leopard geckos and a russian tortoise, and once I get my own place, I will have much more. good luck!