Hey Sally! Usually we don’t refer to our teachers as teachers! We will typically call them Mr/Mrs “Surname” so for example Mrs Smith or Mr Smith. Another way is to refer to a male as “sir” and a female as “ma’am.” This way we don’t always call every single teacher as “teacher.” Hope this helps :)

The title for the most important teacher who e.g. manages the teaching assistants is "head instructor" as opposed to "instructor." You do not use this as a form of address, though, instead calling them by their highest honorific (Dr. [lastname] if they have a doctorate but not a professorship, and Prof. [lastname] if they do have a professorship, otherwise Mx. [lastname])

You might mean Head of Department. Say there are ten maths teachers, but one is in overall charge, they would be Head of the maths department.