Anyways, I teach children with hearing impairments, which means they also have a significant language delay. They didn't know what "coal" was or what "naughty" meant. I had brought in some coal (a gag gift from the Dollar Tree) and they all decided that it was NOT a present they would want. The book provided plenty of examples of what "naughty" meant!
Afterwards we "wrote" (drew pictures) of what it meant to be naughty and nice.
What about you? Do you threaten your kids with reminders like "Santa's watching!!!!" And does it work?