One of the surest ways to lose control of a class is to not follow through on a consequence for a student. Once the class knows that there are no consequences, they will no longer feel the need to behave.
I had one 8th grade teacher leave a movie (Charly). (They had just finished reading excerpts from Flowers for Algernon.) In the lesson plan, she said that I was to warn the classes that if there was any talking, I would turn off the movie and they would have "work" to do. But she did not give me an alternative assignment. The threat was supposed to be enough.
But I know myself. I can't pull off a bluff like that. I need backup, because if I don't have an actual assignment for them, they will sense it.
Just a couple weeks ago, I was sent to cover a class on my prep. They were to watch Jumanji (it was the end of the year). The teacher left me packets of work to give to anyone who wouldn't be silent during the movie.
Several students challenged me. "But we already did that."
My reply: "Oh good, it's review. It'll be easier to do the second time."
I didn't have to send anyone out.
So, for the first class, I came up with an assignment to give them. I never had to use it, though. They must have sensed that I was serious.
Sometimes, they don't take me seriously. There was this one class that I usually try to avoid (I looked for a post about this particular day, but apparently it was too traumatic for me to write about at the time). I knew that I wasn't going to be able to bluff.
These three boys would not stay seated. After too many times out of their seats, I told them that if they got up one more time, they would be out of class with a referral for each. They sat for maybe two minutes. Then some girl walked by the door, and they all had to get up and flirt with her.
They yowled when I gave them their referrals. They had not recalled the previous threat. I had not warned them, they said. But I knew that if I didn't send them out, they would be even worse after this. So, out they went.
It didn't help the class much, but the class didn't get worse.
I've seen what happens when I relent. Suddenly, the student has won. I've lost. It's not a pretty sight. The students know that they can talk me out of it, so they don't need to behave. They have plenty of ready excuses. The class goes downhill fast.
So, no matter how much they beg or plead, when I have threatened a consequence, I have to follow through. And usually I get a thank you or two from the student who was trying to do what he/she was supposed to do all along.