Common core is an approach to curriculum which has proven controversial with both educators and parents. The concept of Common Core is to focus on the elements of education which different subjects share alike. Many teachers recognize the long term benefits of using Common Core but admit it has problems.

Common-Core Survey: Math Teachers Say Parents Are Struggling to Reinforce Skills #dyscalculia
Teachers think Common Core is unrealistic without parent-teacher cooperation.
One such problem is the reliance on parents to supplement the work that teachers do at school. Common Core requires collaboration between parents and teachers and without that collaboration the goals of common core appear to be unrealistic. The Forham Institute examined about 1,000 math teachers and their finding supported these conclusions.
Elementary and middle school math teachers have mixed feelings on the Common Core State Standards, saying both that they set unrealistic expectations and will have long-term benefits, according to the results of a survey by the Thomas B. Fordham Institute.
"Key Takeaways:
Common core can be rewarding in the long run.
Some teachers believe Common Core sets impossible standards.
Common core requires collaboration between parents and teachers.

