This is one of the biggest issues.
The poor behaviour is from a very small number of kids.
Remove those kids and ALL the other kids do better.
If all children are equal, why is the education of these kids less important that the inclusion of the disruptive kids?
This also doesn't address WHY those kids are disruptive. ALL those kids will be disruptive FOR A REASON. The school is unable to cope with them and their needs.
So why are we flogging a dead horse trying to include them?
The kids that suffer most are the quiet ones who are struggling because all the time the teacher has is sucked into dealing with behaviour and not helping them. So the gap between those doing well and those struggling gets bigger for every year at primary. This is made worse as a problem because you can't go off piste from the curriculum. You have to learn certain things each year and there is little capacity to go back and recap on skills that haven't been mastered first time round. These are the building blocks. By the time you leave primary, I'd argue its too late. You aren't functional enough to go to the next level if you haven't got the right foundations.
The issue no one wants to address is how if you fall below a certain point for either behaviour or ability then that setting isn't working for them. There are lots of reasons for this. We really need to stop being so adverse to this, and make provisions for kids who fall into this pattern. That means smaller classes for these kids which costs. But this would benefit everyone and probably stop a lot from falling into the expensive justice system.
Its not a comprehensive education if there are bunch of kids effectively not getting any education because they aren't being served by the system we have.
Flat classes of 30 (or more likely 32 for a lot of kids) is utter madness when you think about it.
We have particularly big schools for Secondary Education too. This can give a wider range of classes but this is at the expense of teachers actually knowing the kids individually and being able to provide an adequate social support.
I think we need a big rethink - and acknowledge of the weaknesses of the current system - with thought about how we can make small changes that have a targetted impact which helps everyone.