This is why I hate it when random people ask children, "Are you excited about Santa Claus?"
The boys that we adopted had NEVER had Christmas prior to being in foster care. They were 3 and 7. They knew about Santa, and just figured that Santa never came to them when they were little because they weren't good. (sigh...still makes me cry)
We made it clear that Santa was a game that parents play with children, that they had done NOTHING wrong, and that Christmas is primarily a time to be grateful for Jesus and for people in your life that you love. This year, at ages 6 and 10, they bought me presents with their own money that they worked for, doing jobs around the house. And you can bet that DH and I showered them with a bunch of fun gifts!
Good for you!
It always bothered me that Santa was raised to a mystical level, and had some traits most identified with Christ.
And then kids find out he's fake.
I would imagine this is around the time they start questioning if there is a G-d.