Especially when the general rule is to communicate via the reading book, the office if a routine matter, or if you must, to speak to the teacher at the end of the school day, and if it's something that takes more than five minutes, make an appointment.
I would expect it in reception, but by Year 3 surely parents should know not to be standing around monopolising the teachers' attention in the morning, delaying the children getting into school. Also (apart from in reception) the kids are meant to line up and the parents stand behind some cones after the bell has gone. Yet some parents still hang around the lines of kids after the bell has gone, sometimes getting in the way of the lines of kids getting into school. It's always the same people you see doing both, in spite of repeated reminders in the newsletters. I often feel sorry for the teaching staff in the mornings & wish that some parents would just let them get on with it (as most do!)