Do you think my teacher was being stupid?

Yesterday, we had a worksheet for homework. My friend needed some answers, and I remembered it wasn't taken for a grade and that meant you were allowed to get help from other people so I gave my paper to her. Meanwhile, we had a substitute teacher for that subject. Her & my science teacher claimed that I was "giving the sub a hard time" because my friend and I were "talking". We weren't even talking, we were just looking at each other! So my science teacher gave us detention for 2 days because I let my friend copy off my paper when my teacher said you were allowed to get help from other people, and because I "gave the substitute a hard time".