I also took this article as aimed at secondary school teachers. Without having to agree with every assertion, I think it has value for them, in terms of promoting more positive attitudes toward math development. And, anecdotally, I have seen some pretty amazing math growth in quite low-functioning students, when taught by a positive, skilled, and relentless math teacher. Including individuals with FSIQs in the 60s who were able to obtain passing scores in algebra I and geometry on state-mandated high school exit exams. Perhaps not coincidentally, the two most effective math teachers I have known were both raised and educated outside of the USA, in cultures with long histories of believing that math (at least high school math) both should be rigorously-taught to, and is within the reach of, all motivated and industrious students.
(Actually, both came from communities where it was not unusual for high school students to have had more advanced math than the average USA high school math teacher has had. But that's another story.)
