I too grew up during the failed US switchover to metric, and I think the approach was all wrong. I remember learning conversions from miles to kilometers, pounds to kilos, etc. That’s not super helpful to embracing new systems.
It’s better to develop an intuitive sense of measurements. When my wife and I did our long walk across Spain we quickly started to understand that 20km was a typical doable day, 15km was an easier day, and 25km was hard. Same thing for buying food in kilos or grams, and whether a temperature forecast was going to be comfortable, hot, or cold. That’s more useful than converting everything to familiar units.
The other thing I remember was how ridiculous the conversions got in terms of significant digits. I mostly saw it on the hiking trails in state and national parks. Someone would basically guess how long the trail was in miles, and then convert it to metric all the way down to the centimeter. The sign would say something like “Forest Loop Trail — 2 miles, 3.21869 km“. Really? That accurate? Why don’t we just call it 3km and consider it good. I don’t think all the digits after the decimal point helped anyone get past the idea that metric units were hard to understand.
