As a teacher librarian, I interrupt classes all the time. Perhaps I should rephrase that, I have to talk to teachers throughout the day. Often I can't talk during teachers' down times of before school or at break because those are busy library times. That said, I remember when I was a classroom teacher and I greatly disliked all the interruptions during class time. Indeed, I had a poster on my classroom door that said if the door was closed, the class wasn't to be interrupted. I would often either take my phone off the hook or turn off the ringer to avoid annoying phone calls during instruction.
It is so important to make sure that I don't bother my colleagues with my constant interruptions. To minimize the impact of my interruptions, I make sure that I very rarely phone a classroom. Over the course of a school day I walk a lot. Actually, that's bit of an understatement. I easily walk my 10,000 steps during the day. I walk to classes because that way I can see where in a lesson a teacher is at. Just walking to the classroom tells me a lot. Door open? Door closed? Lights off? If I can peer in the window, I can see if a teacher is giving instruction or if students are presenting. Walking to classes and chatting with teachers also keeps me connected with staff. I see what's going on in classes and knowing what teachers/students are working on means that I can funnel the right resources to teachers at just the right time.
I think it is imperative for all adults in the school to be respectful of classroom teachers' time. I have to remember that I am not the only person trying to talk to teachers and it simply isn't at all beneficial if my visit creates more harm than good. I have no idea how many interruptions have been before me; I could very well be interruption number seven. By physically going to the classroom, I get an instant vibe. I also get to see what's going on around the school. And I get some exercise.