The Common Core is a set of educational standards for English-language arts and mathematics learning in the United States. These standards attempt to set universal benchmarks for the ways in which critical-thinking, problem-solving, and analytical skills are developed in students, kindergarten to 12th grade, as they prepare to eventually enter college or the workforce.
Each state in the USA can choose whether or not to adopt the Common Core; as of early 2015, 43 states have adopted these standards. The Common Core encourages the inclusion of information about different faith traditions, including Islam, but does not make any value judgments or endorsements. The Common Core exists to improve the standards of American education; one of the ways that it attempts to do so is by allowing for the incorporation of global, cultural content into classrooms.
The Common Core is not a curriculum; it is a set of standards. The way that these standards are realized in different schools is up to the school board/district/teachers themselves–the Common Core does not provide specific educational materials, and does not hold a specific stance on any religion or culture.