What is the difference between "in school" and "at school"? I am a school teacher and are frequently asked "Where are you?" over the cell phone. It's obvious that "I am at work." However, because of the nature of the school evironment, I feel odd replying to the caller that way. I often wonder whether I should say "I am at school" or "I am in school" and not letting people think that I am a student (well, I actually look young and look like a student). In fact, I teach at a college. How should I say and put it right so my reply wouldn't be mistaken as I am still going to school.