Well I do not have a lot of experience in teaching yet, but I agree with the above comments and would add that a instructor's primary role beyond insuring the safety of a flight is to assist the student in teaching himself. If you see it this way rather than as you giving them instruction, you will watch them more carefully for real indications of what are getting and what they are not, and if you let them come to you about how to improve rather than constantly evaluating and judging it stimulates self-evaluation and a genuine desire to improve. Obviously you still have to give critiques and make demands, but even that can be seen as helping them to help their self.
I had a really bad student one time and this poor guy could not make any progress no matter what I or anyone else did for him. He made me realize that the student has to be inherently interested and capable to learn. You are there to assist rather than to dispense wisdom. They won't remember it anyway. The only time I think a teacher really needs to be highly active is when a student gets hung up and by artful presenting the teacher pushes the student see the task in a different, more useful way.