Around 6 or 7. Until I was 8 I lived in NYC. I don't think I ever truly believed in him either. I didn't have a Chimney, I knew he couldn't fit thru the bathroom window and I did not believe that this Caucasion guy (no offense)could be so smooth as to climb up the fire escape in the middle of Harlem and sneak thru any other other windows in the apartment -- unnoticed.
And then I tore open my little piano that I got one year and found a cereal coupon inside. I knew they didn't make
those at the North Pole. Now the tooth fairy was different...
My 5 & 8 year old busted our fascade this year by saying that they found a reciept last year (my 8 year old is incredibly smart and shared the news with his sister). So, we will continue to celebrate the real meaning of xmas, but w/o Santa. However, their gifts will still be a surprise.