"Teach" gives anywhere from .1 to .01 points per interaction (never .15). If the teachers skills are >10 points higher than the level of the student, they will get .1 per interaction. If the skill difference is between 9 and 10 then you get .09 per interaction and so on.
This can be tremendously faster than normal skilling in certain ranges (8-16ish). However, at other levels it is less advantageous.