This UC Berkeley study found detectable differences in the function of the prefrontal cortex (critical for problem solving and creativity) between low-income and higher-income kids. Low frontal lobe response is more likely in kids from low-income families. The authors conclude that environmental factors are tremendously important - simple factors like talking and reading together.

The conclusion is simple: Parents matter a lot. The nurture they provide significantly impacts the brain development of their children - and by consequence their later educational and social opportunities.

Low family income kids also have to be on the lookout to gain an advantage. May mean a full tummy.
High income kids don't have the same pressures.
The value of quality nurture cannot be measured, too high for any scale.