Common Core

Common Core or Common Core State Standards Initiative is a US national set of goals and expectations regarding the K-12 curriculum. States would decide how to meet those goals.

It has turned into a fear-mongering tool for the Right to attack the Left, even though the Left has very little to do with it. Of course, most of the things the right likes to blame the left for have little involvement with the actual left. Most opposition towards it comes from think tanks, charter schools, for-profit colleges/universities, and home schooling parents.

Who is behind it?
Short answer, an independent initiative and not the US Department of Education. The group is called Common Core State Standards Initiative which was developed by the National Governors Association Center for Best Practices (NGA) and the Council of Chief State School Officers (CCSSO).

Louisiana Governor Bobby Jindal was in favor of Common Core but by 2015 had turned to opposing it. Jeb Bush has been a long-term supporter of Common Core but is now avoiding using that phrase.

Opposition
Heritage Foundation hints that Obama is separating parents and children from their education.

Heartland Institute criticizes Common Core on a number of different points, mostly about what they call "erosion of state and local control".

Home School Legal Defense Association has dedicated a movie to the evils of Common Core called "Building the Machine". It's even got a sad kid on the cover for good measure.

Glenn Beck, in his book Conform: Exposing the Truth About Common Core and Public Education. As if the title doesn't have enough fallacy with the reductio ad absurdum of Common Core as "conformity", the book has a, erhm, pretty rotten core of not even wrong claims about Common Core such as: "Since most parents don't understand the Common Core techniques, students are becoming more dependent on their schools and teachers for their education, and less on help from their parents. This is like a dream come true for progressives who hope to continue to minimize the role of parents in the lives of their children."

At this time, Conservapedia is shifting to an anti-Common Core stance.

Subtraction
Perhaps the one element of the proposed Common Core curriculum that has received the most negative attention is the manner in which it teaches certain arithmetic problems. Rather than just teaching the digit-by-digit subtraction algorithm, the Common Core also includes material on understanding the subtraction process and learning certain shortcuts.

This notion made the rounds as a "look at how ridiculous these standards are!", in much the same way the "New Math" did back in the 1960s. The example chosen by the standards' opponents is usually one designed to make the "new way" look ridiculous, such as "32 - 20"; other examples, like "3000 - 1", can instead make the "new way" look good.