Knowledge is complex self and other/s. So anybody who is self-knowledgeable should listen other/s(minds) by discretion. There are 6000 minds in society(knowledge) in three(businessmen/adminstrators,knowledge employees and knowledge workers) economic sections in society.

Teacher should not explain knowledge to all(social).
Knowledge is personal(self).
So teacher by knowing names(faces) and admitting students into classroom of 40 strength should teach knowledge for self and other/s.
That means 1.teacher should not teach in public to all in world and 2.teacher should constantly update knowledge for self by listening students doubts.