My oldest child is six. She has always been taught to distinguish 'real' from 'pretend', and encouraged to decide which is which herself.

She seems to have no problem discovering that something she previously believed is false - at this age there is still so much to learn, and her world view is updating pretty constantly.

What does seem to be distressing for her is finding out that some adults believe things which she has placed solidly in the 'pretend' category. Her teacher's belief in god is particularly perplexing for her.