For almost two decades, the U.S. 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 especially the tests, that most states — including Louisiana — put into place 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 Louisiana adopted in 2010, were the product of a multiyear state-led effort aimed at aligning school expectations with the demands of the real world (both college and modern jobs). The Thomas B. Fordham Institute — the conservative think tank where we examine policy issues and promote reforms in K-12 education — reviewed Louisiana’s old standards and found them to be comparable with the Common Core State Standards in English but significantly worse in math.

And Louisiana also set the bar quite low in the past on state tests by declaring many students to be at a “proficient” level who we really know were far from college and career readiness.

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 the core subjects, and unready for decent-paying jobs. As a result, many were sent to “remediation,” so taxpayers paid twice to educate them. (According to a recent study, Louisianians could have saved some $71 million in 2007-08 on such remediation.)

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

To be clear, our support for Common Core stems from the standards’ quality and little else. We have been, for example, far less supportive of a similar multistate 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 Common Core. It’s appropriate, of course, to worry about threats such as federal intervention into schools, ideological indoctrination of students and poor-quality instruction. 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 Louisiana were elected by the people to ensure that 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 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 Louisianians send their children to schools that are forced to scrap the standards they have spent time and money implementing and move to tests that might be worse?

We welcome debate over Common Core but the facts are clear: Louisiana, 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 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 Louisiana and to ensure that future tests report accurately on how students and schools are doing in relation to these ambitious standards.

Louisiana 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.

Michael J. Petrilli and Michael Brickman are, respectively, executive vice president and national policy director of the Thomas B. Fordham Institute, a right-of-center education policy think tank. Petrilli served in the George W. Bush administration and also is affiliated with the Hoover Institution, while Brickman served as education policy adviser to Wisconsin Gov. Scott Walker.