From "The Teacher Man"

The classroom is a place of high drama. You'll never know what you've done to, or for, the hundreds coming and going. You see them leaving the classroom: dreamy, flat, sneering, admiring, smiling, puzzled. After a few years you developed antennae. You can tell when you've reached them or alienated them. It's chemistry. It's psychology. It's animal instinct. You are with the kids and, as long as you want to be a teacher, there's no escape.Don't expect help from the people who have escaped the classroom, the higher-ups. They're busy going to lunch and thinking higher thoughts. It's you and the kids. So, there's the bell. See you later. Find what you love and do it.

http://ca.youtube.com/watch?v=QiaS64-4I3Y