That reminds me of a Graphics teacher I had in school, he wasn't happy because he took the job as a favour since we had lost both previous teachers, when I say lost I mean they were so crap they were fired. His usual job was at a university, so he was used to a slightly more mature class. Every lesson he would point to something and ask us to identify the material, he used to get really annoyed that in every lesson when he pointed to a workbench and asked what it was made of and everyone kept just saying "wood". My favourite one was when he pointed to a window and said "what's that?" and someone said "where we would all rather be".