We use separate groups for multiple teachers in the same classroom (in Moodlese, "same course"). They're teaching different sections over a very long term. If, for some reason, an instructor can't continue during the term, we move another instructor into the group. If, for some reason, a student needs to be removed from the group, we move the student into another group.
All the student's materials are in the classroom/course and follow the student. This is not the case when moving a student from one classroom/course to another.