I teach 5th grade. Nobody can mention the numbers 6 or 7 without someone saying "6-7". Teacher: Alright, turn to page 6. Students: 6-7. What's your name? 6-7. They use it for everything. Almost like the Smurfs used "smurf" to mean almost anything. Several teachers have banned it in their classrooms. I just try to keep things moving. "Alright, let's look at #6....students: 6-7, me trying to cut them off: yeah, yeah, 6-7, back to what I was saying."