I do not think a teacher should be talking on the cell phone during class. I sub and I keep my phone in my pocket on silent. That way, I know if I get a call. I then check and return the call during a break. It is unprofessional to chat to friends on the phone during class. I agree with the previous poster who compared it to a doctor answering the cell phone during the office visit.
I don't know how I would handle if my son's teacher was chatting during class. I think it would be nice to ask the teacher first. But honestly, does anyone really think that the teacher would say to the parent, "Yes, I talk to my friends every day while your child is in my class." OP - I think it was ok that you contacted the principal. If the teacher just answered one time for an emergency call, she can tell the principal that and all will be fine. If she answering personal calls to chat during class, she now knows that the administration may be watching for this. I guess it also depends on the relationship the OP has with her son's teacher.
I don't know how I would handle if my son's teacher was chatting during class. I think it would be nice to ask the teacher first. But honestly, does anyone really think that the teacher would say to the parent, "Yes, I talk to my friends every day while your child is in my class." OP - I think it was ok that you contacted the principal. If the teacher just answered one time for an emergency call, she can tell the principal that and all will be fine. If she answering personal calls to chat during class, she now knows that the administration may be watching for this. I guess it also depends on the relationship the OP has with her son's teacher.