the word "them" here refers to the teacher
"When the teacher almost catches you cheating so you hit THEM with this move"
you can sub out the word "them" for "he" or "she" depending on the teachers gender, but "them" is a term used when you don't know.
Me: Why did the chicken cross the road?
Friend: I dunno, why?
Me: To get to the idiot's house
Friend: Ok cool, do you have any other jokes?
Me: Knock knock
Friend: Who's there?
Me: The chicken.
