My new school has security cameras installed in the hallways and my class has seen the monitor that shows all of the camera activity. They were FASCINATED by it. Ever the resourceful teacher, I used this newly acquired student-knowledge to my advantage. Instead of explaining that they are security cameras to help keep us safe, I dubbed them "principal cameras" and explained that the principal had the cameras installed to watch students in the hallway. In my defense, I don't make it sound like a bad thing. Instead, it sounds something like "Mrs. M might be watching her cameras. Let's show her our very best hallway walk." That way, it becomes a lie to motivate my students to do the right thing, rather than a lie that implies that someone is waiting to punish anyone that gets out of line (so to speak).
What "little white lie" do you use in the classroom?