And then there were 15...

Originally the idea behind the Common Core curriculum was to establish some sort of national baseline for curriculum so that all states would in essence march to the same drummer.  The idea for Common Core came from the governors of the individual states.   It has never been a federal mandated program.
Next came the idea to assess whether or not students had mastered the skill set of Common Core.  In Maryland Common Core has gotten such a bad reputation that administrators took the label off the can and changed it to College and Career Readiness.   Please note we are still sticking with the CC :)
It didn't take long for the idea of a common assessment to fall away.  Most of the west coast states and the northern tier went with a group called Smarter Balance Consortium.   There are 22 states in that collection.  Some of the New England and Great Lake states went with a consortium known as PARCC, Partnership for Assessment of Readiness for College and Careers.  One state, Pennsylvania, uses both.  Not sure how that is going to work out.
States have been dropping out of PARCC on a consistent basis.  The latest to go is Tennessee.  Its legislature didn't exactly drop PARCC, it just decreed that Tennessee would stay with its own state assessments.  With Tennessee dropping out PARCC is down to 14 states and the District of Columbia.
Fifteen of these United States are choosing none of the above.  The tests are not supposed to be widely used until the 2014-15 school year.   However, this past school year has been the pilot year and there were a number of issues that turned up.
There are multiple reasons advanced for the various state behaviors.   Some states are insisting that they do not want to spend the money on the consortia assessments.  This approach totally ignores the economies of scale that are clear in the group development.   Others are saying that states like Tennessee will be embarrassed when their students are compared to students in Maryland and Massachusetts whose school systems are routinely highly ranked in the country.
All of this begs the question:   Do these assessments, state developed or consortia developed truly measure learning?   That is the big question and so far no one has answered it.