By 13 I was thoroughly confused about religion. Then I became angry. But not because they belived in God, because they were good people. After finding many loopholes in the bible, I decided that there was no God. I decided everything I had learned about religion was for a reason though.
Religion is the ultimate control tool.
I told my friends this and they became very angry, calling me a pagan and telling me that I was going to hell. Well, I made new friends who were much more open, and fellow fans of science. I'm 14 now, and I'm glad to be an atheist. It explains more than the church did, and it's good to know how things work. How christianly of my old friends to try to 'save me' and tell me I was a stupid atheist.