Would you rather be yelled out in front of your friends or talked to 1 on 1 by the teacher? What is more effective? Yelling or lashing out in public (in front of a class or team) only leaves the teacher in a tough position. Anytime someone gets yelled at in front of the class, most of the times the student you are yelling at will now lose respect for you as a teacher and no longer trust what you say as well as lose respect from the class. It's like calling an athlete out in front of the team. It makes the teacher look worse more than the athlete.
When there is a struggle in "public power," two sides both want to look like there in command. For example, when a teacher yells at a student for showing up to class in front of the class, the teacher believes that he/she is setting an example to the rest of the class. He/she also feels like embarrassing the student thinking their point is stronger since people are watching. The student feels threaten and has a urge to fight back. "My previous teacher kept me late." "I was helping a student out with a locker." What this boils down is this: The final say.
The final say or the last concluding remark in the argument is usually the person that wins the argument (not all the time but usually). Having the taste of the final say with no response makes people believe that they out-talked or out-lasted there arguer. This turmoil spirals down into now a short-leash relationship where there is no respect between the two parties and anything they say or do is soon quick triggered with a negative thought.
Teachers need to stop this sense of power because it will only weaken their image and there respect. It is important for students to see the extended care from a teacher. The best thing to do in this situation is to talk privately with the party involved. 1 on 1. Displaying a sense of power in public will escalate until both sides are hurt. Talking to someone in private is more meaningful and shows care. It allows both point of views to be heard and rarely will escalate into further matters. From the example above, if a teacher kept the student after class and expressed that it's really important to show up to class on time and it's disrespectful to the teacher to show up late, this eliminates negative thoughts as the student understands.