My MiL used to speak of similar circumstances in North Bucks, where she lived and taught in the village primary school. In several families teenage girls and their mothers would not be seen for a while and then a new baby would appear in the family registered as the older woman's child, even though she was clearly post menopausal.
In her later teaching years the Local Authority were buying up small terraces of Victorian cottages in the village and housing problem families there. She taught the reception class and would talk of children starting school with little or no language because, in her words, 'they had been talked at, talked over and talked through but never talked to'. She talked of the difficulties of getting children started on reading when some had never seen or held a book or pen, had no vocabulary, couldn't recognise shapes like squares, circles and triangles or understand concepts like 'up' and 'down'. She said it would take two terms to get these children reading ready, leaving her only the summer term to start them reading, not enough for them not to forget over the summer holidays. When they went to the next class it was assumed that they had some reading skills, which they didn't and thus started a pattern of illiteracy and educational failure.