EDMOND, Okla. -- Educators in this Oklahoma City suburb jumped into action when state leaders in 2010 adopted the Common Core academic standards that were sweeping states across the country.

The Edmond school district has a big military population that moves frequently, so officials liked the idea of using the same standards as other states. They also saw Oklahoma’s old standards as inferior. They spent about $500,000 preparing teachers and students, collaborating with educators in other states and buying materials and computers for a new Common Core test, finishing a year in advance.

Then state politicians backtracked, for reasons both financial and political. They dropped plans to give the new test, and during an election campaign in which the standards were hotly debated, they repealed Common Core. Edmond employees came in at the end of the summer last year to rewrite their curriculum again.

“The cost for me in time and training was phenomenally huge,” says Tara Fair, Edmond’s associate superintendent. “That’s one of the things that made me really sick when we went back to the old standards.”

Five years into the biggest transformation of U.S. public education in recent history, Common Core is far from common. Though 45 states initially adopted the shared academic standards in English and math, seven have since repealed or amended them. Among the remaining 38, big disparities remain in what and how students are taught, the materials and technology they use, the preparation of teachers and the tests they are given. A dozen more states are considering revising or abandoning Common Core.

One reason is that Common Core became a hypercharged political issue, with grass-roots movements pressing elected leaders to back off. Some conservatives saw the shared standards as a federal intrusion into state matters, in part because the Obama administration provided grant funding. Some liberals and conservatives decried what they saw as excessive testing and convoluted teaching materials. The standards are a hot topic in the Republican presidential race. Last month, Barack Obama recommended limiting the amount of class time students spend on testing, saying excessive testing “takes the joy out of teaching and learning.”

Click for more from the Wall Street Journal.