Particularly suited to intensive courses and ESP courses, the idea is to give students as much contact as possible with different teaching styles and accents, with each teacher contributing to the learning process with his or her own style.
Obviously requiring a certain amount of co-ordination before, during and after the course, it provides a unique opportunity for teachers to confirm whether learning/assimilation is actually taking place by seeing the results of their colleagues' input, and adjusting accordingly, presenting possibly similar material in a different way without it seeming repetitive for the students. Another reason for co-ordinating is to avoid repetition, unless going over previously-taught input actually forms part of the activity programmed.
By rotating the teacher, ideally every 90 minutes in the case of intensive courses, often but not always coinciding with natural breaks in the day, students feel more motivated and refreshed and very much appreciate the change in routine.
The inevitable comparison of good-cop/bad-cop also helps to maintain what Caine and Caine (1994) refer to as the necessary state of relaxed alertness in the students, as team teaching contributes to the perfect balance between students feeling themselves challenged on the one hand, but relaxed and not threatened, on the other.