I've never subbed before, but just last month my school has a new policy with subs. It used to be that the subs would just take their lunch and free periods in the teacher workrooms, where most of the teachers do. The subs received a memo that due to confidentiality concerns, this is no longer permitted, and they should have their lunch and prep periods in the cafeteria and/or the media center. My guess is that since many of the subs are parents of students in the school, some teachers were worried in case they were discussing a student in workroom in the presence of someone who would bring that information to the parent (i.e. a friend of the parent). I don't know for sure though as it was never really explained other than "confidentiality". I personally don't love this policy as it seems exclusionary and makes the subs seem lesser. Does your district have a similar policy?