Karen's teacher maintains a book that records every instance of misconduct by her students. Every time a student misbehaves, she adds a point against his or her name in the book. Karen's students now stop misbehaving in class because they fear that the teacher will add points against their names. This is an example of

What Karen's is doing by adding a point against the name of the students who misbehave is simply punishment.

She is using punishment as a means to give negative feedback when a student displays unproper behavior, with the hope that the punishment will condition students to behave well.

And according to the information in the question, the punishment is working.