Off the top of my head: DOMS being little crystals in muscles, tongue having separate areas for each type of taste, food pyramid, blue blood in the veins, the appendix being useless, body temperature doesn't change disregarding whether it's exposed to cold or to heat, and a whole lot of stuff related to politics and history I'd rather just omit (I don't live in the US).
All things I learned in school which were wrong information.
Not to mention, the current state of education is far worse. I don't think most realize how low the bar is.
One of my teachers in elementary school told us that people in the Arabic world wore long garments because as Muslims, they believed the Messiah would be born by a male, and thus, it was important to have something to catch the baby as it unexpectedly popped out one day and would otherwise hit the ground.
She only really had two faults: She wasn't very bright, and she wasn't fond of children. I had her in about 80% of all my classes for six years. High school was a relief.
It may interest you to know that this was a misremembered truth.
It is widely believed by their neighbors, that the _Druze_ wear baggy pants because they believe that the Mahdi will be born to a male, and the pants will catch the baby etc. I say "widely believed", the Druze are famously secretive and will not confirm or deny most things about their religion. The 'elect' Druze men do wear distinctive baggy trousers with the crotch down around the knees: no one else does.
The Druze are people in the Arabic world: moreover, they are Arabs. They began as an Isma'ili sect, but do not identify as Muslim: they call themselves al-Muwaḥḥidūn, meaning 'the monotheists', or 'unitarians'.
Much closer to correct than not!
My biology teacher in school once tried to teach us that winds created by God. Not like spiritually or something but that God literally made the wind I guess.
My “earth sciences” teacher also once tried to argue with me against the universal law of gravitation. (no, she was not referring to Special/General Relativity. She didn’t agree two objects in a vacuum fall at the same speed regardless of mass.