The children are so often such wonderful people, and so are the parents. The children respect you and look up to you, and that doesn't happen elsewhere. They're good because they feel they're loved, and cared for genuinely as human beings. I sometimes suspect the problems in the schools of some areas are caused because there aren't enough people who are getting through to the students that they are cared about. The message the response conveys is exactly the opposite from what a teacher wants to convey.
Most punishment reinforces the bad behavior.
It makes the student feel rejected and unwanted. The only way I've found that students permanently change is if they have the feeling of being cared for. The last thing you want to do is fall into the trap that the negative student is setting up for you. If you do, he'll play out his role as rebel, and you'll play out your role as authoritarian, and you'll both be miserable. Punishment doesn't change behavior.