I was working at urban elementary school as an assistant principal. Most of my time was spent dealing with pretty heavy disciplinary issues (I certainly wasn't any sort of instructional leader). I was walking through the hallway and a kindergarten class was coming from the other direction. The teacher stopped me and pulled me aside. She explained, with a little smile, that one of her students had called another student a 'bitch.' She wasn't going to bother me with it, but since I was passing by, could I talk to her. "Sure."
I pulled the little peanut out of line and crouched down next to her. She did the typical little girl bit which entails putting your head down with a very sad face (by the way- this works!). I asked her what she did, and she confessed that she had said a bad word. Her sister was model 5th grader in the building, so I next asked, "Do you hear your sister using words like that?" With her head still down, she shook her sad little had back and forth and stood silently.
After a long pause, she lifted her head, looked me in the eyes and said- "But my mommy says it all the time!"