If the superintendents of failing school districts were as adept at fixing schools as they are at making excuses for their poor performance, America would have the best education system in the world.

Instead, the just-released tests administered by the Program for International Student Assessment show that other countries are making faster progress than the United States.

Our teenagers are now ranked 26th in math, 21st in science and 17th in reading. Shanghai, Singapore, South Korea, and Hong Kong are leading the pack.

In the face of this powerful proof of their failure, school superintendents and other education leaders blithely blame someone else for U.S. stagnation.

“The problem we find in American education isn’t that schools are ‘falling behind,’ it is that schools are ‘pulling apart,’” said the American Association of School Administrators.

“Poverty in America is the real issue behind today’s education gap, and it means students can experience different education trajectories because of where they live,” the association said.

Certainly, many children from low-income, single-parent households lack the same family support for their education that children with two wealthier parents enjoy.

But the United States is not the only nation with poor kids. As a close look at the data from PISA reveals, the income gap in the United States does not explain the inability of our schools to teach our students basic math, science and reading skills.

If everything is fine except that the poor are dragging down the average, the United States would be turning out the same share of high-performing students as other countries.

To the contrary, only 9 percent of U.S. students perform at the highest proficiency levels in math, far behind the 20 to 30 percent performing at that level in countries such as Korea, Japan, Switzerland and the Netherlands.

Our neighbor to the north, Canada, turns out almost twice as many high-flyers as the United States.

Moreover, if an income gap made America unique, you would expect the percentage of American students performing well below proficiency in math to be much higher than the percentage of low performers in countries with average test scores similar to the United States.

But that’s not the case. We have the same average scores as Slovakia, Lithuania and Hungary (hardly a group with which we want to be compared!), and like those countries’ students, about a quarter of our students performed well below proficiency in math.

In other words, the United States is no worse at educating our weakest students than are countries with scores similar to ours.

The problems in American education are across the board, with every kind of student doing poorly when compared to students in other industrialized countries.

For the first time in history, countries like Poland and Ireland are educating their children better than the United States.

These are countries from which millions of immigrants once braved oceans and uncertainty to come to America so their children would have the opportunity for a better life.

Now, kids in those countries have a better chance of being intellectually equipped for a modern, global economy than do kids in the United States.

Unfortunately, America’s education malaise can only get worse when the professionals we pay to run our schools refuse to take any responsibility for the situation.

They are like the general who blames his equipment, or complains about the weather, or says his lieutenants blew the battle.

When that noise emanates from headquarters, one knows that the next battle is likely to be even worse — unless new leadership is put in place.

It is time for superintendents to man-up, admit their mistakes and take charge of the education of the students for whom they are responsible.

If that is not done, the country as a whole will pay the penalty, because our economy will grow at a far slower rate than it would if we fixed our failing schools.

Studies in our recently released book show that reaching Canada’s performance level would increase our workers’ incomes by an average of 20 percent.

That growth would be a tremendous aid in balancing the federal budget without raising taxes or cutting spending.

Of course, it would also begin to take care of the poverty that superintendents are so fond of calling “the real issue” behind the mediocre public education in the United States.

Eric Hanushek is a senior fellow at the Hoover Institution of Stanford University, and Paul Peterson is professor of government at Harvard University.

This editorial originally appeared in the Washington Examiner.