Being brought up as a Christian, I used to think that Christianity taught people 'good' things eg. don't steal, don't kill, don't lie, while all other religions (Hinduism, Buddism) encouraged these things.
A childhood belief about church

others believed things like this
- I used to believe God had a pet tortoise. There was a hymn we sang that went "Great things he hath taught us"— Lozza
- I used to believe that if you weren't good, the Trix Rabbit would steal your yogurt.— Kyle
- On this site when people sign "Anon" I thought Anon was one person who believed in a lot of weird things...— Slow to catch on.
- I used to believe that you could pass things down the telephone.Anon
- I used to believe that when you lost things, it sometimes was because they had really vanished. — fluffy
- I used to think that when you get older you could go back and redo things. — cobra