The teacher can fill this jar with cotton balls or marbles each time they notice the class is being good (quiet in the halls/class, good job during a lesson, etc.) and when the jar is full the class gets some sort of reward (no homework for a night, cookies, etc.). This emphasizes the good things the students do instead of always pointing out the bad and gives them incentive to behave! I had something like this in my 4th grade class and as a student I thought it was great as positive reinforcement!
Great Site!
This stoplight is great for monitoring students' behavior in the classroom. I had one in my first grade classroom, each time a student acted out they moved their clothespin to yellow and if they acted out even more they moved it to red. When the student reached red they had to "sit on the wall" at recess and could not play. I would definitely use this in my classroom!
(This site has other great classroom ideas)