I remember when I was in elementary school (even a few years before the US officially passed the law requiring a switch to the Metric system), the teacher would spend quite a lot of time instructing us on using the Metric System in place of the Imperial system of measurements. It rolled off our backs like water off that of a duck. None of us picked it up, and they gave up trying. Seems like that was in either my Fourth or Fifth Grade, so 1970-1972.