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.