Well, according to the training I went through, the ideal thing is for learning to be collaborative, which does not necessarily mean equal. For language acquisition, the teacher is supposed to guide the learner such that the learner has the context to form or make connections between language points. The idea is that by making a student work for understanding, the student will therefore retain the language better.
However, it's often difficult to provide enough context to elicit and guide responses, especially when students expect a teacher-centric model of learning where the teacher is there to do drills and be copied.
Anyway, my earlier point was, as a teacher, I don't know what my student knows and I am often unfamiliar with their cultures, languages and personal difficulties. In that aspect, I have little control, so to be effective I have to learn as much about my students as quickly as I can so that I can figure out how best to help them. I think ideally, most of the work should be done by the student, but the teacher has to work really hard to get that to happen.