Yeah, the old "punish everyone in the class" ploy. The teacher doesn't really want to punish everyone, they just want the old peer pressure to force someone to tattle on who really did it. It's a bad tactic because it almost never works and every minute that goes by makes the teacher look weaker and weaker and every moment that goes by without anyone tattling makes it less and less likely that anyone ever will. All the teacher is doing with this tactic is clearly demonstrating how little control they actually have over their class.
I train student teachers all the time, and I always make them memorize the Ten Commandments Of Classroom Discipline.
1. Thou Shalt Not Make Empty Threats. If you say you are going to do something, then do it. if you say that Jimmy loses recess if he talks during a quiz, and he talks, Jimmy damn well better not be outside for recess. Otherwise little Jimmy now owns you. Make no threats or promises of discipline you are not ready and willing and have the authority to follow through on. If classroom teachers do not have the power to suspend a student (and almost none of them do....), then you do NOT threaten a student with suspension. It just makes you look stupid.
2. Thou Shalt Deal With The Disease, Not the Symptom. Students will misbehave for an infinite number of reasons, but they will only misbehave in a finite number of ways. This means that the same behavior is often motivated by vastly different reasons, and you can not treat every instance of a behavior the same. You must identify why a behavior is occurring before you can intervene to stop the behavior on a long term basis. If all you ever do is deal with the behavior itself, you will continue to deal with it all year. By all means issue consequences for the behavior, but deal with the cause at your first opportunity. If you can not determine causes of behavior, try another profession.
3. Thou Shalt Be Consistent. Students, unlike Vroomfondle and Magicthighs, do not thrive on doubt and uncertainty. They must know that if certain behaviors are performed that are against your clearly defined rules, that certain consequences will be issued. These consequences must be consistent from day to day. Something that rates 2 demerits on Monday can not become 10 on Friday when your nerves are frazzled. Likewise something you issued a detention for on Tuesday can not be ignored on Thursday, It does not matter how busy you are, you must stop and deal with it.
4. Thou Shalt Make Them Wait For It. There is no need to issue consequences immediately for a behavior. Your students are not puppies; they possess the capacity to connect a delayed consequence with a previous behavior. If you are uncertain about what to do about a certain behavior, look momentarily grim, inform the student you will need to think about it and will inform them of your decision tomorrow, then shake you head sadly and go on with the lesson. Occasionally throughout the day gaze over at them and sigh before jotting something down on a pad of paper. A good teacher can make the wait to find out the consequence far worse than the consequence itself. (I have had students beg me to just give them detentions. I smile sadly and say, "I'll think about it. Can I tell you tomorrow?")
5. Thou Shalt Not Demand a Rat. Want to know the fastest way to turn a class against you? Hold the entire class responsible for the actions of a few in an attempt to get peer pressure to reveal who did it. It never works. You either get the Class Martyr to theatrically admit to it just to end the Mexican stand off or you get a silent, sullen room of students who are now in about the worst state of mind you can possibly be to learn. If no one rats out the culprit in the first 30 seconds, the odds of them doing it at all are very remote, and if no one does, you just look like a jackass. A weak, powerless jackass. The students will not be angry at the student whose actions put them in this position....they will be angry at the teacher. Congratulations! You have now lost the class.
6. Thou Shalt Be Confident. Project confidence. Show no fear. If you are going to be wrong, be wrong strong. If students come up to you to admit something that they did, let them assume from your responses and body language that you already knew what they had done and were just waiting for them to come admit it to you.....even if you had no idea that they had even done anything at all. If someone confesses to you that they were the culprit in a mysterious misbehavior....make them think you already knew. A good teacher can play this game so well that students begin to suspect some kind of mutant mind reading is going on. (I once had students spend an hour at lunch searching my classroom for the hidden cameras they were convinced must be there.)
7. Thou Shalt Not Need No Steenking Badges. An appeal to higher authority, the principal, another teacher, whoever, surrenders your authority, and the students sense this. Once you have started relying on an outside authority (or the threat of an outside authority), you will generally have to continue relying on them. Congratulations! You are no longer the master of your classroom, and have probably become the Principal's least favorite faculty member. Only appeal to a higher authority when it is absolutely necessary.
8. Thou Shalt Not Wed Thyself To A Specific Method. If what you are doing is not working, change it. Never be so committed to a specific methodology that you can not break free from it if it is ineffective. It doesn't matter if it worked for the last 10 years, if it isn't working now, change it.
9. Thou Shalt Not Measure Thy Manhood (Or Womanhood) Against Thy Student's. No pissing contests with students. You do not debate with students about discipline, you do not argue with them. Feel free to discuss these matters with them when they (and you) are calm, but know the difference between a discussion and an argument and do not allow yourself to be drawn into the latter. Do not negotiate or make deals with students on matters of discipline, this implies that you are equals in status on the matter. You are not equals when it comes to discipline: you are in charge.
10. Thou Shalt Not Humiliate Thy Students. You do not hold students up for ridicule or public humiliation. A lot of teachers use humiliation techniques every day, mocking or disparaging their students over behavior or academic failures. This is a very bad idea. You know what you get when you humiliate a student with a behavior problem? You get a pissed off student who still has the original behavior problem. Nice job, Sherlock. Way to make your day more difficult. A quite word in private is always better than a loud word in public.