Most parents seem to have confused Common Core standards with curriculum designed (at least supposedly designed) to help students meet those standards. For example, one of the fourth grade math common core standards is
Solve multistep word problems posed with whole numbers and having whole-number answers using the four operations, including problems in which remainders must be interpreted. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding.Nowhere in the above statement is it dictated to the teacher how to teach anything. It just states what the student should be able to do by the end of fourth grade. Think of it like the set of requirements in a Boy Scout or Girl Scout handbook for a certain rank. Distilled to the main point, this is what the Common Core standard is all about. It sets goals for each grade level.
Unfortunately most of what is touted by the talking heads on TV and shared on Facebook as Common Core, actually deals with curriculum and not the standards. Curriculum is usually set by the local school district or sometimes the state. Because of their size, California and Texas has a tendency to push the direction the US goes on curriculum because the textbook vendors cater to the largest customers. As you can see above, the standards don't say HOW to teach a subject, just what the expected outcome should be.
For example, today on the radio, one of the talk radio hosts was ranting because his daughter had been taught three ways to do subtraction and one of them was confusing her. The particular method that she was struggling with was subtraction by addition or "method of complements". The idea behind this method is to make mental math easier. One example of this method in every day life is a skill that a lot of people no longer have because of cash registers.... how to count back change.
The bottom line is that a common set of goals for every student in the United States is NOT a bad thing. In fact goals are good things and give us a way to quantitatively evaluate educational policies such as curriculum. Unfortunately text book writers and local curriculum directors have used the Common Core as an excuse to try new methodologies as experiments on our students. Hopefully over time the failed curriculum choices made will be phased out. In the mean time, don't vilify the teachers for teaching what they're told to teach by their management. Instead educate yourself on the curriculum and the standards and lobby your school board and administration to make needed changes so that every student in every school in the United States can excel.