For students, it is embarrassing to have the phone ring in class and then the teacher sends you out of the room. Make your students more comfortable by filling out a phone memo to tell them where and when to go when they get called out during the period. In my room, I use this also as their hall pass to where they have been called. I simply write the time and date in the corner and sign my initials. I often fill out the pass at the phone and carry it nonchalantly with me to drop at the student's desk without calling attention to what the phone interruption was for.