Let's face it. We can teach you the theory, the history, etc. We can teach you how to develop curriculum, write appropriate lesson plans, help you to understand the needs of different learners, use assessments wisely, etc. But there are some things we can never teach you how to do. We can tell you our own experiences, we can brainstorm solutions. But, it's all different once you are out in the real world.
I could talk about some of what I've learned as a teacher, but I'd rather share the reflections of a second year teacher here. I came across this a few minutes ago. It's worth the read. And it really does the job of posing an important question: What is the relationship between schools and US society?