I don't totally agree with your last bit, there are many schools that have associated SEN centres within the normal school structure, the consequence can be that some of the children that have quite debilitating issues that might cause some disruption even with a 'one to one' whilst becoming...
I am not sure I am totally with you on that, especially in the primary age group.
I have always found that the truly disruptive pupils are likely to have genuine special needs, they're simply incapable of conforming to any 'usual' school behaviour requirements.
Then those that are/become...
The learning environment you seem to be advocating not only allowed systematic abuse, but also the reason why we are unlikely to know just how widespread it was.