When I was in 4th grade (in 1979), growing up in the US, we learned about the metric system. My teacher said that we were learning it, because the US would soon be switching over to it.

I came home and told my mother what my teacher had said. And my mother responded, "Yes, that's what my teacher told me in 4th grade, also."

Fast forward more than 30 years, and the US is no closer, despite other countries (such as England and Canada) having pulled off smooth transitions. Aside from a few signs on a highway in Massachusetts (of course) that I saw 20 years ago, marked in km as well as miles, and 2-liter bottles of soda, the metric system has completely and utterly failed in the US.

I now live in Israel, where the metric system is standard. My children cannot believe that I once used a system that wasn't so simple and standardized. But because they're not learning the metric system, but just using it, they never learned the beauty of its design, with powers of 10, and uniform prefixes. They just know how many cm tall they are, how much is in a 1 kg container of ice cream, and how many km it is to their grandparents' house.

It seems obvious to me that the metric system can and should be uniform, including in the US. But there is so much inertia, and so much history of opposing it, and so much technology tied up with the existing English system, that I don't realistically see it happening anytime soon, even if it could and should happen.