Ask Me A Question!
I tell all my students on the first day of class, that if I hear a student speaking to their seat partner when I am speaking (who has not raised her or his hand), then that MUST mean they have a question about something that I said in english that they don`t understand! (my students are highschool students in francophone Quebec). The student then has to ask me a question IN ENGLISH- any question! This gets the students` attention! Once a few of the noisy ones go through the embarrasment of having to formulate a question off ``the tops of their heads`` in front of the class, there is generally less whispering in french amongst friends in class.
--Quebec