A new international study on student performance in reading, math and science has once again demonstrated that the U.S. might be the world's richest and most powerful country, but its achievements in education do not rank quite as highly.

The Onion, a satirical outlet that often spins off the news, responded with an item bearing this headline: "Slovenian 8th-Graders Surprised Even They Outperformed U.S. Students In Science." It's a funny way of drawing attention to the U.S.'s perennial under-performance in global education rankings. But it's also a bit misguided.

Implicit in the Onion story is the assumption that education rankings should roughly correlate with national wealth and prestige. There's something to this: education costs money, and the U.S. is the richest country on Earth. The U.S. is also a world leader in technology and innovation, which would seem to suggest that education is a high priority. So the perennially disappointing U.S. education rankings are a real story. But there's something that stories highlighting America's relatively low rankings on these sorts of indices often seem to miss: Maintaining national high standards is a lot more difficult when that nation includes 311 million people. The U.S. has the world's third-largest population, which also happens to be diverse and geographically quite disparate. That U.S. national student averages are relatively low is partially a function of U.S. education policies and results, yes, but it's also a function of the fact that those averages pull from a data set that's more than 150 times the size of little Slovenia's.

Slovenia's growth and modernization in the two decades since it broke away from Yugoslavia is indeed impressive. But it's also a country of 2 million. Designing and executing education policy for 2 million people, even if their average income is half of America's, is a whole different category of a challenge than is designing policy for 311 million.

Imagine you are a teacher. You know that you will be judged not on how many students you educate but on your students' average test score. Do you choose to run a classroom of two or a classroom of 311? Probably the former. But if a rival teacher takes the 311-student classroom and produces an average test score just below yours, then your rival is arguably a more successful educator. After all, the rival's classroom, statistically speaking, almost certainly produced many students who scored better than your two did.

Now for the obvious question: Who cares? It's just a silly Onion article, after all.

Two reasons: first, because this is a common misconception in how people perceive the U.S.'  frequently low rankings on international comparisons, and the Onion just happened to hit it. Again, none of this is to dismiss the very real concerns about U.S. education policy and effectiveness that are well-chronicled by people much smarter than myself. But, because of the U.S.' enormous size, comparing national averages to much smaller societies can be quite misleading.

And second, because the Onion's satire, particularly on foreign policy, is typically quite perceptive and often surprisingly good at cutting to the heart of a major issue. For example: Chinese soft power is often clumsy, the troops fighting in Afghanistan are increasingly distant from the terrorist attack that got them there, atrocities in Syria are not inspiring much reaction from Americans, public awareness of the Afghan war is low, the U.S. military is focusing on winding down the troubled war, and few expected Libya to remain a beacon of freedom for long after Moammar Gaddafi's fall. That's a strong record of foreign policy commentary-by-way-of-satire, and you hate to see the Onion dropping the ball.