Across the country, what was once bipartisan consensus around national standards has collapsed into acrimony about the Common Core, with states dropping out of the two national tests tied to it that had been the centerpiece of the Obama administration’s education strategy.

But no about-face has resonated more than the one in Massachusetts, for years a leader in education reform. This state embraced uniform standards and tests with consequences more than two decades before the Common Core, and by 2005, its children led all states in the National Assessment of Educational Progress, often called the nation’s report card, and rose above all other countries, save Singapore, in science.

The state’s participation was seen as validation of the Common Core and the multistate test; Dr. Chester became the chairman of the board that oversees the test Massachusetts joined. The state’s rejection of that test sounded the bell on common assessments, signaling that the future will now look much like the past — with more tests, but almost no ability to compare the difference between one state and another.

“It’s hugely symbolic because Massachusetts is widely seen as kind of the gold standard in successful education reform,” said Morgan Polikoff, an assistant professor of education at the University of Southern California, who is leading an evaluation of the national tests. “It opens the door for a lot of other states that are under a lot of pressure to repeal Common Core. Getting rid of these tests is a nice bone to throw.”

The fight in Massachusetts has been dizzying, with a strange alliance between the teachers’ union and a conservative think tank that years before had been a chief proponent of the state’s earlier drive for standards and high-stakes tests. As in other states, conservatives complained of federal overreach into local schooling, while the union objected to tying the tests to teacher evaluations. The debate drew money from national political players like the billionaire David Koch and the Bill & Melinda Gates Foundation.