I think you could replace 'math' with pretty much any endeavour and the article would still ring true.
As a musician, I've heard so many people say "I'd love to be able to play [instrument], but I just don't have musical talent", when in reality it was caused by an uninspiring teacher, or lack of practise.
"For high school math, inborn talent is just much less important than hard work, preparation, and self-confidence." This statement from the article is essentially correct, and is well backed up by comparative studies of mathematics education using different instructional methods in the United States, and especially by international comparisons in mathematics education.
My current work is teaching advanced mathematics classes to elementary-age learners in a supplemental program (year-round, locally) and advising parents on the education of precocious learners of mathematics (two weeks each summer, as part of an international summer program). So I try to keep up with the voluminous research on mathematics education. Learner attitudes are crucial. The job of a teacher is to help build successful learner attitudes.
For parents, I have posted online a set of FAQs on mathematics instruction,
with the FAQs intended to help parents impart to their children attitudes and study habits that will build more success in learning mathematics. The level of mathematics expected of learners in United States senior high schools is not particularly hard--it is the level expected of junior-high-school students in several parts of east Asia and some parts of Europe. But initial poor preparation in mathematics in elementary school[1] often hobbles United States learners as they grow up into high school age.
As a musician, I've heard so many people say "I'd love to be able to play [instrument], but I just don't have musical talent", when in reality it was caused by an uninspiring teacher, or lack of practise.