This whole thread is desperately sad, and I don't think that this is an attack on class or wealth.
I don't know of children in this situation in my DC's school, I do know of extended family members whose DC still slept in a cot, wore a nappy and couldn't use a knife and fork at Reception age. NOT from a council estate, from a "nice" neighbourhood.
Oh and my eldest has one filling (had it aged 4), apparently those packs of sultanas are buggers when children have weak enamel. He'd only ever drank milk/water/dliuted fruit juice and rarely had sweets.
If a teacher came round to my house she'd see lots of lego etc but very few books downstairs, all the books are upstairs, the DC call it their library.
I do not doubt that there are children living awful lives and that some parents are negligent/ill educated, but some of the markers are a bit shite and I really do not think that bad parenting is the prevail of those living in "sink estates". The woman most likely to turn up pissed at school collection was the richest (and I mean v wealthy) when I was last doing school pick ups.
Bad/ill informed parenting can be anywhere.