The Common Core — effectively national math and English curriculum standards coming soon to a school near you — is supposed to be a new, higher bar that will take the United States from the academic doldrums to international dominance.

So why is there so much unhappiness about it? There didn’t seem to be much just three years ago. Back then, state school boards and governors were sprinting to adopt the Core. In practically the blink of an eye, 45 states had signed on.

But states weren’t leaping because they couldn’t resist the Core’s academic magnetism. They were leaping because it was the Great Recession — and the Obama administration was dangling a $4.35 billion Race to the Top carrot in front of them. Big points in that federal program were awarded for adopting the Core, so, with little public debate, most did.

Major displeasure has come only recently, because only recently has implementation hit the district level. And that means moms, dads and other citizens have recently gotten a crash course in the Core.

Their opposition has been sudden and potent — with several states now considering legislation to either slow or end implementation, and Indiana, Pennsylvania and Michigan having officially paused it.

There are good reasons a backlash is now in full swing.

First, creation and adoption of these standards has violated the traditions of open debate and citizen control that are supposed to undergird public schooling.

Though preliminary drafts of the standards were released to the public, the standards were written behind closed doors by the National Governors Association and the Council of Chief State School Officers — private organizations — and copyrighted. There is also no public record of the meetings available.

Adoption was then strong-armed by the Obama administration via Race to the Top and No Child Left Behind waivers that the feds granted states.

Second, the Core claims to be “internationally benchmarked,” but supporters can’t name a country to which it is pegged. In addition, according to Stanford mathematician James Milgram, the math standards would put kids two years behind their top-scoring international peers by grade seven.

Third, there is little evidence that setting national standards yields superior outcomes. Supporters argue that most countries that beat us on international exams have national standards. True, but so do most countries that finish below us.

There is little deeper research on this, but what there is suggests that once you control for variables such as income and culture, national standards have no effect.

Fourth, our root problem isn’t poor standards, but bad political incentives. The groups with the most at stake in the education system will be most motivated to be involved in its politics, and those are the professional education associations, education schools, state and federal bureaucrats and other interests whose livelihoods come from it.

They are also more organized than parents, making it easier to exert pressure on school boards and legislatures. Combine these factors with their natural incentives — not to be forced to hit high bars — and too-low standards typically result.

Fifth, making standards uniform across the country reduces the benefits of competition between states and districts, which vie to attract residents and businesses. That stifles laboratories of democracy.

Most troubling of all, the Common Core will cripple individual choice, which is highly concerning because all children are unique and need different things. Supposedly autonomous charter schools, which already must use state standards, will become far more similar to one another.

Many religious schools — either because they’ve swallowed the line that the standards are rigorous or because they feel they must use them to show they get superior results — have adopted the Core. And with tests like the SAT and GED being aligned to the standards, even homeschoolers will be sucked in.

What do Core supporters have to say about all these concerns? After being pummeled for weeks, they are fighting back — but their strategy has largely been to smear opponents as dopes or kooks.

Too common is the type of thing former Obama adviser David Axelrod recently tweeted after reading that the Core was galvanizing the Tea Party: “This is truly idiotic. Our competitors around the world must be laughing.”

Actually, what’s idiotic is implementing national standards without real scrutiny or debate. Hopefully, it’s not too late.