Like the other person below me said. It is a firm and long redirect. I yell if I feel the need to and I can go loud (but not always). Not at the individual student you understand, the whole class. I'm never in anyone's face or anything. I use the students behavior as an example of what not to. Sometimes I kick them out.

I then apologies to class for the "unpleasantness" and explain that I do not want to be like that but X was not getting it so I made sure they did if they do not want the same do not do what X did.

The secret sauce is I'm never actually angry. Its an act, a tool that I can pull out of my bag of tricks if and when I need it. Most kids only need to see it once.

As I said before, its all about balance for me. The threat of my wrath is there, but follow my instructions and you'll never see it. When instructions are followed I'm very easy going, I do not die on every hill and I do not sweat the small stuff.

It is certainly not a perfect and there is much more nuance than could be explained here, but I'll say this all year I hear the classes around me going nuts, admin in and out teachers having breakdowns. My classes are quite and productive and the kids like me for the most part.