This honestly happened to me once actually "studied" for geology and when I got to the classroom I found out that we were having a sience test not geology what I was thinking
When I was taking my AP calc test it specifically said in the instructions that calculators would be provided so I didn't bring one. I pointed it out and raged that it was BS I was being short-changed for being the only person who actually read.
Still got a 3.
Still got a 3.