From the article: '"There is a denial phenomenon," says Prof Peterson. He said the tendency to make internal comparisons between different groups within the US had shielded the country from recognising how much they are being overtaken by international rivals. "The American public has been trained to think about white versus minority, urban versus suburban, rich versus poor," he said.'"
But let's take a closer look at the information in the article and see if this way of thinking about it makes sense.
Southern states Mississippi, Alabama and Louisiana are among the weakest performers, with results similar to developing countries such as Kazakhstan and Thailand. [...] If Massachusetts had been considered as a separate entity it would have been the seventh best at maths in the world. Minnesota, Vermont, New Jersey and Montana are all high performers.
There are some clear patterns here. The low-performing states like Mississippi, Alabama, and Louisiana are poor, rural, and have large minority populations. Conversely, Minnesota, New Jersey, and Massachusetts are wealthy, urbanized states with relatively low minority populations. So maybe thinking about scholastic achievement issues in terms of "white versus minority, urban versus suburban, rich versus poor" makes quite a bit of sense after all.