How we change what others think, feel, believe and do
Losing control of yourself is the first stage in losing control of the class. For some children this is scary. For many others, it is entertainment. If they can provoke a teacher into losing their rag then they will do it again and again until the teacher has a nervous breakdown.
The first sign of losing it will be in how you feel. Typically this will include negative emotions including fear and anger. Strong emotions cause the thinking parts of the brain to shut down as they force you into reactions you may later regret.
Strong feelings may start small for example with mild frustration. This is the point at which to catch things and do some serious self-talk to bring yourself down before you take off.
Some children are very good at spotting the first signs and pushing a wedge into even the smallest crack. You have to decide early on who is in charge of your emotions (and it had better be you).
Emotions carry easily in your voice, which can broadcast loudly when you are relaxed and when you are aroused and angry.
There is a terrible temptation that some teachers fall into, which is to shout. It may even work for the first few times as the shock affects the children, but before long they will get used to it you will just get hoarse. The simplest rule is never to raise your voice, other than the normal 'teacher's voice' that carries well to the back of the classroom.
You should also never plead with children to behave, as this will be taken as another sign you are losing control. If you use the word 'please', do so in a commanding tone, not in a way that offers choice.
What you can do with your voice is to send deliberate signals, for example by slightly raising it as an indicator that the next response will be positive and controlled action.
Beyond your voice, your body language will send loud signals about how you are feeling. It can be tempting to use dominant or aggressive body language, but be very careful here, as you may provoke a situation you cannot handle without getting into trouble.
The last ditch of stress is a physical response that is typically some variation on the fight-or-flight reaction. Hitting children for any reason can get you sacked these days, which means the provocateurs win. Breakdown in front of the class is also a losing strategy.
At worst if you're feeling close to the edge, getting out of the room is better than the alternatives. Just walk out. Stand outside and take a breather. If necessary, get some help in. It is a part of every school's duty to support beleaguered teachers.