Hello from London. I started questioning the existence of all powerful deities while at school, a Catholic school. The more stuff they tried to indoctrinate me with, the more I seemed to question it. Even at that young age I could see what they were teaching us didn't add up. I would say I have held an atheist perspective on life since the age of about nine or ten.
I suppose I'm lucky in that I live in a country where it seems the majority of the people I come into contact with, seem to hold the similar view regarding the existence of a god, that it's just an antiquated system designed by man to control man, nothing more, nothing less.
If I could say one good thing about my Catholic school education, that would be that all my friends from those days are atheists too, so if anything, my particular Catholic school seems a very good vehicle for producing the opposite of what they hoped for.