When I was 5, my mom told me it wasn't real. I accepted it well from what I remember but my father got pissed off when she told me the truth about Santa.
He's not real? NOOOOOOO! Honestly, though, I noticed a Walmart sticker on one of my presents. Then my mother took my letter to Santa and never mailed it. I put two and two together and felt very smug about it.
On my own. I basically figured that his supposedly accomplished feats are physically impossible. Plus my parents never really tried to imply that he was real either. XD
When my parents were telling my brother that Sana isn't real, he's like "wait... so Santa isn't real?" and my parents said "well, it's the spirit of santa and giving and christmas..."and my brother is like "O.o SANTA IS A GHOST!!?"
Though it may be surprising, I don't remember at all. I asked my parents if they told me or somebody else did, but they don't know. This is something that's intrigued me because most of the people remember and I don't.
I heard my parents brining the gifts up from the basement. So I don't believe in him but I don't let them know that so I will still get gifts. Ha ha lol