Larry Cuban shares a very thoughtful perspective on the answer to this question at his “Thoughts On Teaching” post. I’d strongly encourage you to read his entire post. Here’s an excerpt:

Missing in all of the talk and mandates aimed at improving teacher quality are the traditional moral obligations of teaching the young be they preschoolers or graduate students….

Let me be more specific about what I mean by traditions of teaching imposing moral obligations upon the teacher. Teaching obliges those who teach kindergartners, sixth graders, molecular biology, auto mechanics, or art to give sustained intellectual and moral attention to students’ learning and growth. Intellectual attentiveness means concentrating on what students know, feel, and think about the content and skills to be learned–the technical side of teaching–but then go on to deepen their understanding of the world and their capacity to continue learning.

Moral attentiveness means to concentrate on helping students grow as persons in grace and sensitivity, becoming more rather than less thoughtful about ideas, becoming more rather than less respectful of others’ views, and becoming more rather than less responsible for reducing social injustice. Questions of what is fair, right, and just arise constantly in classrooms; students learn moral sensibilities from how their teachers answer those questions…