People who had someone condescendingly explain something that they didn't know you're an expert on, what happened?

Had a math teacher who didn’t know wtf she was talking about when it came to geometry. Luckily my dad is a mathematician with several PhDs and awards under his belt. He explained proofs to me and five of my friends the day before the test and we all went in super confident. Lo and behold we had all gotten the proofs section wrong. My dad took a look at the test and said her formatting and grading were bunk and she clearly didn’t understand proofs (I wish I could explain more but I’ve completely forgotten). He came in after school one day to talk to her about the test.

After going back and forth for a while (and her refusing to admit she was mistaken), she said that she had graded it according to the textbook and pulled out her grading manual to try and show him. He told her that wasn’t how the problems were intended to be set or graded and she said “so you’re saying you know more then the textbook authors?”. I wasn’t in the room, but to this day my Dad doubles over laughing while recounting the look on her face when he, completely silently, turns to the title page and points to own name in the front of the book.

/r/AskReddit Thread