Right, thanks very much. Very interesting
I can see the points raised have merit. I do believe sometimes these days every child has to be classified, especially those in need. In my day you had those considered plain thick. That was wrong and thankfully more is now recognised however you will still always have levels of intelligence and no amount of education will help some. We can't all be brain surgeons. Inherited intellect is proven, two people of lower intelligence are unlikely, though not always, to have a highly intelligent child. Because poorer people have less opportunity to a good education and are less likely to be transient, their lives are almost mapped out for them at birth. This does mean the gene pool from where they come from is smaller and the inherited issues are continued and in fact become compounded.
Interestingly these issues, though often hidden, were also suffered by the upper classes in the 19th century where they would procreate between a very small population. The royals of many countries, all being related, suffered, many with mental health issues.