Exposure to various environmental residuals? Tobacco, alcohol, and marijuana could be more prevalent in the environment of a poor child, at least in the living conditions that the child is directly in contact with at a very young age.
Yes. That is a factor.
I think we’re all tiptoeing around another very real genetic possibility.
Statistically, a greater number of a certain race, we’re constantly reminded, are poor. If members of that race had consistently smaller brains than another race that tended to be wealthier, couldn’t wealth be misinterpreted as the causal factor of lower intelligence, rather than an effect?
Of course saying so is anathema in our PC world, but if we’re to honestly assess the situation, shouldn’t it at least be considered?