I am a teacher now. In my first year. It's hard. I have to find a place to write. Sometimes my students get upset when I ask them things they shouldn't know. There's a reason, I try to get them to use their brains! I really enjoyed watching this video made by a math teacher. It shows what happens when students aren't challenged this way often enough! Many times this leaves student frustrated, and if there's a grade attached to these sort of assessments they get angry. So perhaps it's best to leave this as a learning experience instead of an assignment. This raises the question though, is there something wrong with asking a student a question outside of the box?