So, primitive hunter-gatherers who have never been inside a classroom score as high on geometry as American children who are being "educated" at $10,000 per head per year.
To be fair, the comparison was for 6-year-olds. Not many 6-year-olds are getting any kind of "education" beyond how to sit at their desks, color within the lines, and playing well with others. The "$10,000 per head" education comes when they get older.
Now let's compare the abilities of the US students versus the hunter-gathers on, say, trigonometry when they're 18.
I didn't get that the U.S. students were six; I understood it to include hunter-gatherers from the age of six on.