First this: here, we don't really have "Santa". It is ST.Nicolas who brings toys to the kids, at December 6th

Here is the interesting info:
http://www-astro.physics.ox.ac.uk/~e...ml#explanation

I found out at age 10 that it was not true. I was VERY mad, and yelled "so, doesn't God exist too then???". My parents reasured me that it was just St.Nicolas who was fake . Phew!!!
I think kids should be told whenever they ask for it, at least before they are 8. It is sad when they find out to soon too.
My son also was told by his teacher when he was only 7. Oh my, I was mad too then!!