Of course you don’t know. You don’t know because only *I* know. If you knew and I didn’t know, then you’d be teaching me instead of me teaching you – and for a student to be teaching his teacher is presumptuous and rude. Do I make myself clear? — Willy Wonka and the Chocolate Factory

I never taught anyone anything without learning something myself. A teacher who gets insulted when a student asks the question he can’t answer or shows the teacher something she’s never seen before is not doing their job.