It can be frustrating for a principal when a teacher or couple of teachers refers students to the office for anything and everything. The most frustrating thing about the situation is that the principal understands that the teacher has no respect from his/her students. When a teacher doesn't handle any discipline situations it actually undermines their own authority. Kids are smart and they are more likely to respect a teacher who handles their own discipline problems the majority of the time.
It is a good idea to create a teacher's guide to discipline referrals. This lists your expectations on whether the teacher should handle the situation or send them to you on a referral. This will ultimately make your job easier and it will take all the guess work out for the teacher.