I really thought I made it clear to my students that if they really needed to use their cell phones they need to exit the classroom. They are only to use them if it is an emergency. Students try to hide their phones while they are texting. We could be in the middle of a classroom discussion and they are called upon and of course they don't have any clue what topic we are on. What can I do to show I really don't like phones on in my class?