I stopped believing in Santa fairly young and the reason was that I worked it out for myself. I had heard the rumors and wasn’t sure… so I conducted an experiment. I was… I don’t remember, let’s say between 4 and 6 and leave it at that.
Anyway, the year previous I received a tiger model/toy. I was pretty rough on toys as a kid, especially toys I loved and I loved that tiger. By November or so of next year it was just broken shards of plastic or completely gone. I wanted another. Between that and my doubts about Santa (which I was keeping very close to my vest) I decided to carry out an experiment.
I whispered the same thing to every single store Santa I saw. I wrote the same thing o every “letter” to Santa. The message was “I want a tiger like I got last year!”. I didn’t tell my parents or even my brother.
On Christmas morning (actually about three in the morning when my brother woke on Christmas) I ran out and although there were lots of great toys…. there was no tiger.
And that was that. There was no Santa, my parents had been getting those toys (all credit to them, they had a real knack in picking out stuff we would enjoy).
I went through the motions of believing in Santa for another couple years but my heart wasn’t in it.