DS1 is in Y1. He came home yesterday saying that they'd learned about Christopher Columbus, and how everyone was against his trip because they thought the world was flat. I told him that that wasn't true, and that people had known for a long time before that the world is round. I'm wondering if I should write a note to his teacher to point out the error. I know it's not particularly important in the grand scheme of things, but it is a pervasive myth and it leaves children with the impression that people then were a bit stupid. So AIBU?