By failing at reading comprehension. There's a vast difference between public school students and school-aged children. In Chicago, only 10% of public school students are white[1], with a 45% white population[2] (for example.) Conflating the two things seems almost willfully deceptive.
What's wilfully deceptive is pointing to one city and claiming it is relevant to national statistics. The WP Article assets a majority of public school students IN THE US are in poverty, that is objectively false. So the reading comprehension problem isn't with the article I cited.
The WP article isn't really central to my point -- that outside factors have more to do with poor math performance than anything happening inside the schools. I worked in a public school as a tutor for kids slightly behind their grade level (not with the kids who were really struggling) and I have plenty of anecdata from that experience. Kids with drug-addicted parents, kids with parents in prison, kids not having enough food at night, medicated kids, obese kids, a kid who had to move mid school year because his house was shot up in a driveby, etc.