In one of the math classes I teach, there are adults from China, Haiti, Ethiopia, Brazil, Colombia, and an array of other countries. The group is about as diverse as you can imagine, but the one thing everyone has in common is familiarity with the metric system. That should make my job easier, right? Problem is, I teach in the U.S., where the old imperial English system of measurement still reigns supreme.

So, in our little classroom in Massachusetts, students have to learn clunky units like ounces, gallons, inches, and feet so they can navigate daily life in America. I try to make the class fun by including bits of history and other anecdotes: speculation that the foot was derived from the length of a man's actual foot or the allure of ordering a pint of beer at an American watering hole. Still, learning imperial units takes time away from lessons on higher-order skills and on the English vocabulary for universal math concepts such as exponents and square roots.

Inevitably, students ask me why Americans continue to use the old system. Most are surprised to learn that even the English have given up on it. That's when I walk us over to the classroom map and ask the group how many nations other than the U.S. still use ounces and inches. Guesses are usually in the neighborhood of 10 or 15. When I reveal that the answer is two, they immediately assume that Canada and Australia are the holdouts. The correct answers, though, are Liberia and Myanmar, which we then proceed to find on the map. Perplexed, students cock their heads and ask again, this time with concern, why in the world Americans continue to use the old system.

My answer begins with a bit of history. The U.S. officially recognized the metric system way back in 1866, but it has since only nudged its citizens toward change. I personally remember halfhearted interest in "the switch to metric" when I was in elementary school, shortly after the toothless Metric Conversion Act of 1975 was passed. But, despite small subsequent steps such as the Fair Packaging and Labeling Act of 1994 (which requires metric units merely to be placed alongside English units on consumer products), progress toward a wholesale shift has largely stagnated. In 2009, most Americans whose jobs don't demand use of metric units have little concept of a gram or a meter, much less an appreciation for a system based elegantly on the number 10. In short, we haven't been forced to change.

Back in the classroom, as I stand before the world map with students from every corner of the globe, America's competitive disadvantage in math and science is palpable, and I honestly feel a little embarrassed. The failure of the U.S. to fully integrate the metric system obviously did not cause that disadvantage, but American resistance to metric units is, in my view, an ugly symptom of the problem. Perhaps my student from Bangladesh (a neighbor of Myanmar) puts it best: "It is the 21st century, yes?"