Remember when Pluto was a planet? Did you grow up being told that dinosaurs were slow, cold-blooded dull lizards (in my own defense, i never believed this one)? Remember when the moon had no water? Name the countries that make up Africa.
The things we know as 'fact' change. Knowledge is not a constant. This is very exciting albeit a little inconvenient for school text book publishers. It is also slightly inconvenient for those amongst us who fondly remember the good old days when schooling was about learning facts and useful stuff that you could demonstrate your mastery over via direct recall.
Samuel Arbesman introduces the concept of the mesofact. In the Boston Globe, he writes: "When people think of knowledge, they generally think of two sorts of facts: facts that don’t change, like the height of Mount Everest or the capital of the United States, and facts that fluctuate constantly, like the temperature or the stock market close. But in between there is a third kind: facts that change slowly. These are facts which we tend to view as fixed, but which shift over the course of a lifetime". Read the article here. Visit mesofacts.org here. I very much like the concept although i'm not sure that his example of a capital city and a mountain are good examples of facts that don't change.