It's not what you teach, 

it's how you teach it.

It's an ultimate goal of a teach to, ensure that students develop the knowledge, understanding, and skill necessary to be fulfilled and productive members of society. -Chapter 5 Fulfilling the promise of the differentiated classroom

With that being said there are 2 types of teachers.  The teachers that teach, and the teachers that teach you.  Both teachers most likely know the content that they are teaching, they both are most likely experts in the subject/subjects that they are teaching, The difference between those two teachers is this: 

One teacher, "The information is here.  I'll deliver it. You get it."  

The other teacher, "I will learn about you and do whatever t takes, using this subject matter, to make sure you are a fuller and more potent human being than you were when you walked in this room.  Please be my colleague in that quest."

Which teacher do you want to be?  I think we all know the answer to that.  This quote explains what this student said the difference was between these two teachers, "The difference was that the first teacher taught algebra.  The second teacher taught me German."  

If we are just teaching to teach, our students are not learning.

I would like to share an experience that I had in high school.  I had a teacher for math my first semester of my junior year.  It seemed to me like I was learning nothing.  The teacher would teach, and students in the back of the class were totally checked out, and were doing other things.  The teacher knew math, and taught math everyday of that semester but that didn't mean that I learned any math.  As the semester changed my math teacher changed as well.  Oddly to my surprise I really started to understand everything in that math class.  It was the way that the teacher taught that changed my understanding.  It was the same math class, and there were two teachers teaching EXACTLY the same content, but one of those teachers was teaching math, and the other was teaching ME math.  Something in that class changed the way that I viewed math.  As I came into my senior year, I had enough math credits that I wasn't required to take math, and as good as that idea sounded I signed up for a college prep math class from the same teacher that I had for my second semester of my junior year.  That year was no different than the semester before.  I learned SO much.  As I began taking college math classes just the next year there was so much that I already knew, and I owe that all to the teacher 

who taught ME math.