Just as I feel that long division has been tossed out incorrectly, I also feel that the teaching of grammar (what's that) has gone by the wayside, especially its art of diagramming sentences.
An article from the New York Times by Kitty Burns Florey (see here) from June 2012, referring to diagramming sentences, says "First of all, diagramming is not for everyone." That hits our problem nail on the head, especially when compared with the term "Common Core": what we teach in our schools now is supposed to be for everyone.
In my experience as both a student and a teacher, what our public schools have failed to acknowledge is that there are some items that are beneficial to some, not for all, and that it is okay to teach some things in the classroom that not all students can master.
We put all New York students through Algebra 1 (whatever it is called now), force them through it all, calling them failures when there are parts they cannot handle. Those "failures" become negative marks on both the students' and teachers' records, and generally on the students' home lives as well as we pass the buck to such things as single parent families and poverty.
What New York should be looking at are two key issues: are students' ready to learn what they are being taught? Does everybody need to master what they are taught? If we were all to recognize that some skills that need to be known and can be learned by some, but not necessarily by all, then it would be okay for a student to not succeed at that skill. Can you imagine students' getting things wrong in school and being told "that's okay."
We do it in PE quite masterfully. We take all through basketball, football, baseball, soccer, etc., identify those who want to do well and can do well, and proceed with them. We do not condemn the others and call them failures.
We have gone through a patch in the last 25 years where knowledge and skills obtainable by few have slowly been weaned out of our curriculum. This has been a downward trend. The Common Core will not change this trend.
I recommend reading "Common Core Standards Will Impose an Unproven ‘One Size Fits All’ Curriculum on North Carolina" (get it here). This article says "Common Core Standards have been sold as a tool to raise academic standards and improve education for all students across America. However, an untested assumption underlies CCS: all students should learn the same things and have the same education."
The Common Core standards website says "The standards promote equity by ensuring all students, no matter where they live, are well prepared with the skills and knowledge necessary to collaborate and compete with their peers in the United States and abroad." Take note that equity can be obtained by bringing down the top as ell as raising the bottom. Also take note that it says "no matter where they live". Really? ANYwhere?