I can't remember being told or not told that he was real....and I can't recall being told he wasn't real. I think it was just a thing that happened over the years....I knew that there was no possible way he could get presents to everyone everywhere in the space of one night.
I do recall going outside with my parents one christmas eve right when i was about 6 and being shown a single, shining star in the sky....they said it was the star of bethlehem, and I believed them.
Nowadays. ....we give gifts to our kids, and when they were small we used to leave milk and cookies out for santa. That's changed now, and he gets a mince pie (british thing) and a finger of single malt irish. A couple of years, D and i went outside after they had gone to bed and threw rocks on the roof to imitate reindeer hooves alighting on the shingles. He does a pretty good baritone "ho ho ho....meeeerrrrrryyy christmas"...!!