I don’t think there is any room for a teacher to shout in anger at their students in the classroom (or outside of it to be honest). We need to find other ways of making sure the students behave. With adults, I don’t think there is a problem, but with teenagers, of course, it is a different story.
One method which I think works quite well, and doesn’t make the teacher out to be the bad guy, is peer discipline. The following idea is similar to the “five point deduction” idea, if you have heard of it…
Write on the board:
Let’s have a good lesson today. On Friday we want to play a game.
(game, song, watch a film etc…. whatever you do as a treat with your students)
Leave this on the board for the whole lesson.
Explain to the students that you want to play a game with them on Friday, but each time they misbehave, you are going to cross off a letter. If it is impossible to understand the sentence at the end of the lesson, you won’t be playing a game, but continuing with your regular work (grammar, reading, etc…)
The students will then begin to tow the line with the rowdy students, and tell them to be quiet and behave, so you have very little to do by way of discipline.
Who needs any extra stress?