If it happens routinely, it's because the child or children doing it has/have an issue - an issue that needs dealing with.
It won't be 'bullying' - if it's routine, it'll be something quite deep, affecting the child's ability to act within social norms inside school.
Ideally, the CT, working with the SENDCO, will try and organise means of mediating the behaviour - and if those interventions don't work, other professional expertise will be called in and drawn on.
Bottom line: if violent, disruptive behaviour is routinely going on, it's a huge problem for everyone in the class. There's at least one child in the class that - for whatever reason - can't cope. There's a class of stressed children (they will be stressed - how would you feel?) - and the disruptive behaviour will ripple out in a domino effect amongst the other children. Ultimately, you have a teacher who is no longer able to teach fully effectively, and a class where only the most resilient and fully-focussed children are really learning.
Now, the thing is, this is the point where school cuts have a huge impact. Ideally, there should be interventions going on to change that behaviour and to mediate it: extra adults in the class-room, other adults in to see what the root of the problem is, expert knowledge available to work in ways to change the behaviour, bandwidth in the system that allows the time - paid time, delivered by paid adults - to deliver all this.
But ... cuts.
So ... back to you ...
How long has this been going on? Is it getting any better?
It's a sad, sad truth - and one that parents don't really know (not yet, anyway,) - that the cuts have opened huge rifts between schools. It's not fair. And the experience in offer at School A can be radically different to that on offer in School B.
You may well be at School A, where the school are dealing with this, and the issue will be sorted out
You won't be told what is being done - quite rightly : it's confidential. But things are being done, and done well.
Or you can be at School B, which is buckling under the strain of the cuts, has serious issues delivering learning to children in under-resourced classes ('resources' doesn't just mean pens and pencils - it also means professional help to support challenged and challenging students) and where a Class Teacher is struggling trying to deliver learning in a disrupted environment, with little or no support.
It's hard to tell which is which from the outside. Clues will be how long this goes on for, whether there's a high turn-over of staff.
I'm beginning to feel very bleak and angry about the cuts.
Long -term, I think people need to speak out. Short-term, I think if you're in a school that really isn't coping, you should seriously look for one that is coping.
But ... none of the above may be relevant.
Your child may well be in a school that is simply dealing with the issue confidentially, and it will be resolved, albeit not immediately.