Hi, Mawkish,
I have been teaching in both primary and secondary schools for years, so I know what you're talking about. It can be tough, and there are some children and some situations which can't be resolved peacefully and positively. Australian schools, in general, are happy and relaxed compared to what we see and hear about tough schools in the UK and 'normal' schools in the US

but even so, I know of situations where teachers have had to employ considerable physical force, and times when police have been called.
The most difficult situations, in my experience, are created by kids with psychological problems (and, often, learning difficulties): when they are crazy, they are unpredictable and often unreachable.
So, what to do?
Best practice for me is Right Speech, supported by compassion. More generally, maintaining good positive relationships with as many members of the school community as possible (that includes parents as well as colleagues and children) gives you strength and moral support (physical support, too, if it comes to that) in any conflict situation.
Teaching can be challenging but is, in the long run, one of the most rewarding occupations. Stick to it!
All the best,
Kim