The teacher left the final for the class with a brief note. The final was 100 questions, multiple choice. I was to read out the answers to the final, but I was not to read out the letter of the correct choice. It was very clear in the note, but sometimes I miss things.
I read out the first question and then I read out "A" followed by the answer. Then I saw what the students had. They had a study guide with all the questions but none of the answer choices. (I heard a couple students whispering, "She's giving us the answers," which clued me in.) They were to have gone through the questions, found the answers, and my job was to help them check to make sure they got the correct answers on their study guides.
It happens. I screw up sometimes. I misread the lesson plans or I misinterpret something, and I do it wrong. That's when I have to pay attention to the class--they usually clue me in to my mistake.
Once I caught my mistake, I made sure not to read out the letter answer. I only read out the first one, so that's one point I gave them (out of 100 won't impact their scores that much). And it sure got the class's attention, so that's a bonus.
I made sure to own up to my mistake in my note to the teacher. It's not the worst thing that's ever happened while I was subbing for him. That would be the fight between two girls (actual punches thrown), but that's another story.