The point stands that the vast majority of schoolkids aren't going to be cadets.
Quite simply, we shouldn't have this kind of 'unofficial discipline' in schools. That's the teacher's job, and other students shouldn't be taking these measures. For this reason, it's not ethically sound. If you're punishing a majority of kids who didn't do anything wrong, that's not fair. And don't give me that 'well life is unfair' rubbish, because the truth is that things can be fairer. We should argue for things to improve, because, well, they can.
And we shouldn't be running our schools like we do the military. It's a different kettle of fish. Soldiers have to be prepared to go into warzones. Pupils sit exams. Whatever a student intends on doing later on in life, it's not the school's responsibility to get them into the Royal Marines. It's the school's responsibility to get them through their GCSEs.
I have quite a few gripes with our exam system, though it'd be off-topic to voice them here.
I also disagree that it's effective. It's not. From my experiences, it doesn't actually dissuade people from doing things because people are still willing to do them. I've suffered enough group punishments to realise that. If group punishments were truly effective, then you wouldn't need many of them. Those implementing them want those being punished to have a bad time so that the perpetrator(s) stop doing whatever they're doing out of fear of it happening again. But often, the perpetrator(s) just don't care. They'd do it again.
It's definitely not ethically sound, and while I accept it is a futile endeavour to try to change the minds of people who are much older and grew up in an environment that is different in many respects, I've made my opinions clear that it's not actually effective, either. In my experiences, it's the preserve of lazy Games teachers who get hacked off when a couple of the foreign students start speaking in Chinese and can't be bothered to punish the right people. And then they'd still speak Chinese next lesson, too. If you disagree then fine, disagree all the hell you want. But I'm not willing to defend group punishments.
And yes, I know that's not a thesis. It was a joke, DaleCooper.
What a terrible teacher. And yes, I am thinking of a worse word than 'terrible'.