Some of the comments here refer to a period of "reform math" instruction BEFORE the introduction of the Common Core State Standards in mathematics,[2] which are actually quite recent. Implementation of the Common Core in school classrooms in the United States is only a year or two old today. The Common Core was an attempt to introduce coherency and logical progression into the mishmash of topics that characterized "reform math" textbooks such as Everyday Math (which is probably the best and most mathematically sound of the reform math textbooks) and TERC: Investigations, among other titles. The Common Core standards are generally regarded, as curriculum standards, as a plain improvement over what most states set as mathematics curriculum standards before.[3] On the other hand, many of the mathematics who criticized the preceding period of "reform math" instruction (basically most United States school practice in the twenty-first century) think that the current Common Core textbooks and teacher training courses still don't go far enough in improving instruction.
As a parent, I expect and welcome school instruction in any topic that is better and more research-based than what I received as a child. The quotations from parents in the article kindly submitted here along the lines of "Why should my child be expected to learn things I don't understand?" seems like a very bizarre approach to parenting to me. (As a homeschooling parent, I used the Miquon Math[4] and Singapore Primary Mathematics series[5] with great success in helping my four children learn their elementary mathematics. They have been able to go on to more advanced mathematics study with relative ease. I had to learn new topics and new techniques to use those materials, but that is good for me. I was lucky that my wife, educated in Taiwan, largely understands the approach taken in the Singapore materials, but so far both of our older two sons have gone well beyond the mathematics study level of either of their parents. Education is supposed to improve from generation to generation, or what are schools for? (That's why we homeschool--we lay a good foundation for our children with the best available curricular materials to get them ready for classes with teachers who know what they are doing for our children's secondary education.)
[1] http://www.theatlantic.com/education/archive/2014/04/confusi...
[2] http://www.corestandards.org/Math/
[3] http://educationnext.org/the-common-core-math-standards/
[5] http://www.singaporemath.com/Primary_Mathematics_US_Ed_s/39....