I got the book “Holding the Center – Sanctuary in a Time of Confusion” by Richard Strozzi-Heckler recently. I finally picked it up to begin reading it last night, and randomly opened it to this paragraph, in the chapter on Teachership:

“The kanji for sensei is a man leading an ox by a nose ring. This indicates that through wisdom and intelligence a teacher is able to guide even that which is difficult and resistant. Sen depicts the earth giving birth to a plant, which in turn yields a flower or fruit. From this image we are reminded that life comes from life, that learning and growth come from a living transmission. Sei is often spoken of as Heaven, Human, and Earth united to create something new and useful. With the symbols placed together, sensei or teacher is someone who has more experience than us, whose consciousness is more expanded, who has walked before us on the path that we are now on, and who embodies a vision of the world that is more powerful than the one we now live in. Sensei is able to guide students on the steps that are necessary for them to gain proficiency in a specific discourse. A teacher is someone willing to cultivate our own life so that it will bear fruit." 

While the explanation of the symbols escapes me, the sentiment rings true. The entire chapter is a very interesting look at what it is to be a teacher.