Had something similar in an english class back in 6th grade (Brazil, 12yo students) - I knew some english words better than her and I wish I was making it up. She would say to class that checkers is chess game, call muffins doughnuts and vice versa (and say it like "dougonoot"). Of course, she always ignored my corrections and told me I was wrong whenever she could, like with checkers (she probably assumed that because "checkered" translates to "xadrez" despite the meaning there being for the texture/stamp, an adjective, rather than the game "xadrez", a noun)

So, one bright day, she gives us an exam where the first 10 or so questions are just True or False according to the text. I read the text, I read the questions and notice that they don't reference the text at all. I quietly ask her if the text is right, because several words being referenced in the question are nowhere in the text and she just dismisses me, "Just read and you'll find the answers", so I sit back slightly pissed and do what every other student did: randomly guess. Next week, we receive the exams back with our grades, another kid asks the teacher if she could show where in the text the answers for the T/F questions were. She starts reading and realizes her mistake. "Sorry class, I forgot the second half of the text" - which was a total lie because "second half" implies that at least something would have used the first half. I guess she learned how to revise her exams, because the others we had during the year were fine.

Anyway, if you ever wonder why most Brazilians know jack shit about English, it's because the mandatory English classes are fucking shit. My conspiracy theory headcanon is that this is on purpose to sell extracurricular English courses