British Classroom Culture

British elementary schools are fairly structured in their day-to-day activities, which is similar to that of the US. But, students are constantly moving in-and-out of the classroom. They have piano lessons, choir rehearsal, are being taken out to work with another teacher, etc. It is rare for every student to be in the class at once. And this is normal to the classroom. The teacher thinks nothing of it when a student walks out of the classroom. It is a bizarre system to me and I have stopped trying to understand what is going on at all times. Another interesting British classroom culture quirk that I have found is the way they share scores (marks). It is typical for students to yell out their scores for the teacher to record it. In general, they are very open about who is higher and who is lower in the class. That would not be the case in the US. Each student would be responsible for only his/her work and scores. Should the students be competing against the other students in the class or should they be competing with only themselves to make improvements?