I learned about the number of bones in sixth grade. I remember exactly the day because after the presentation we had, it was a special day about health and science, they asked some review questions. One of them was "Does the child human body have more or less bones than the adult human body?" Everyone else said less, and I raised my hand and said more.
I was really proud I got it right, because it meant I listened. It also makes more sense when you think about it, because I don't see how our bones could somehow increase in number when we got older, unless we broke some.