Good post from GreenTulips.
I'd dislike the idea if it were used to make uninformed assumptions about all children living in deprivation.
I don't mind the idea if it is coming from a place that recognises that children living in poverty face additional challenges and more should be demanded from society as a whole to support children living in poverty.
As many have said, behaviour is a form of communication; 'poor' behaviour is often communicating a whole lot of stuff a child doesn't have any other means of communicating. It may also be 'poor' behaviour in that it doesn't fit with the norms of a school (and may be poor socialisation or related to SEND-related inability to fit with those norms).
In that first category (and in the second for a lot of reasons) fall many - not all but quite a few, children who are living in poverty - and those children do often live in areas that are geographical pockets of poverty.
Those children have to contend with all sorts. Hunger is real, terrible accommodation, stressed parents who are dealing with poverty-related issues, really big stuff (family members dead through gang violence and parents in jail through the same), MH issues in parents (which is also poverty-related).
How well do you think you - an adult - would deal with all of that?
The amazing thing is that children are amazingly resilient and many children will try so very hard to please adults - including those in schools.
It's probably a good time to point out that the government has cut access to free school meals for a whole swathe of the child population. 6,000 in my borough alone.
How's that going to help with behaviour?