For almost two decades, the United States has been working to improve its schools by holding them accountable for results on standardized tests. And there’s been some success, with America’s lowest-performing students showing marked gains.

Unfortunately, similar progress hasn’t been made for students in the middle or at the top. That shouldn’t be surprising, since the standards and tests that most states put into place — including in Georgia — were set at ridiculously low levels. The federal No Child Left Behind Act, in fact, encouraged this behavior by demanding that states aim to get 100 percent of their students to the “proficient” level by 2014 — but let the states define proficiency.

The Common Core State Standards, which Georgia adopted in 2010, were the product of a multi-year state-led effort aimed at aligning school expectations for students with the demands of the real world (both college and modern jobs). The Thomas B. Fordham Institute — a conservative think tank where we examine policy issues and promote reforms in k-12 education — reviewed Georgia’s old standards as well as the Common Core and found them to be comparable.

Yet Georgia also set the bar quite low in the past by declaring many students at a “proficient” level who we really knew to be performing at just a basic or even below basic level on core English and mathematics skills.

Now we see the result of these short-sighted policies: Many young people have been taking and passing these standardized tests, yet still emerge from high school unready for college-level work in core subjects, and unready for decent-paying jobs. As a result, many have been sent to “remediation,” so taxpayers have paid twice to educate them. (According to a recent study, Georgia taxpayers could have saved some $75 million in 2007-08 on such remediation.)

We have long advocated for higher, clearer school standards that focus on essential skills and vital knowledge to prepare students to be productive, self-sufficient citizens. We also believe that key education decisions belong with states, communities, teachers and parents, and were therefore glad that the Common Core limited its work to standards and did not push into curriculum or instruction.

To be clear, our support for the Common Core stems from the standards’ quality and little else. We have been, for example, far less supportive of a similar multi-state effort around science standards because we fear the final product is less worthy of adoption.

In recent months, we have been puzzled by the small but vocal minority of conservatives who have joined forces with some on the far left to oppose the Common Core. It’s appropriate, of course, to worry about threats like federal intervention into schools, ideological indoctrination of students, and poor-quality instruction.

But the Common Core doesn’t promote any of those things. Instead, it pushes schools, teachers and students to higher levels of achievement and deeper levels of skill-and-content knowledge than most have accomplished in the past.

Leaders in Georgia were elected by the people to ensure the billions of taxpayer dollars spent on public education are used effectively and efficiently to educate our next generation. These officials should now stand up to misguided and ill-informed political attacks and demand answers from both liberal and conservative critics of the Common Core: Would those on the left really remove testing and other measures that ensure parents and teachers know whether students are learning all that they should — and how to help those who aren’t?

Would those on the right really have Georgians send their children to schools that are forced to scrap the standards they have spent time and money implementing and move to ones that might be worse?

We welcome debate over the Common Core, but the facts are clear: Georgia, to its credit, has opted to raise expectations for student learning. Opponents have an obligation to say what they would do instead. If someone offers a better option, we will support it. If states choose to use flexibility built into the Common Core to improve their standards even more, we will support that, too.

In the meantime, however, something very promising is on the table. Attention and energy should go into devising the best way to put it into practice in Georgia and to ensure future tests report accurately on how students and schools are doing in relation to these ambitious standards.

Georgia made a choice for the better when it adopted the Common Core. It should not turn back now, especially under pressure from a few loud opponents without a better plan.