Okay I have just read this on another thread but this is a statement I hear quite a lot and want to ask the question.
If all you teach your child is atheism how will they make their mind up about religion when they grow up because they have no religion other than atheism?
They will know nothing other than what you have taught them so they have nothing to make their mind up about - they will be atheist, by default. If people genuinely want their children to make their own mind up they have to provide them with a reasonable alternative (ie, Judaism / Christianity / Islam).
I don't actually know any adults who have been brought up atheist who have thought all of a sudden "I believe in God, I am going to go to Church".