A couple of things. While I don't doubt that the listed difference in height is accurate, the picture capitalizes on an optical illusion which makes the already significant height difference seem even more dramatic. Here, look again:
Dream Time said:
Earl Boykins 5'5
Yao Ming 7'4
Note Ming's feet, which appear to be "lower" than Boykins's. He's clearly standing in the foreground, perhaps several meters from Boykins. To get a better idea of how they would look standing next to each other, visualize
twice the vertical difference between the base of Ming's and Boykins's respective feet. Now subtract that from Ming's height.
(Ming will still be considerably taller than Boykins, of course! But thinking about it like this might help overcome the exaggerated impression we're given from the picture.)
Also, with regards to the use of the metric system (SI) in US schools, the NCTM (National Council of Teachers of Mathematics) has long recommended that all state and county math curricula place an emphasis on teaching SI alongside the English Standard (ES) system in the early grades (see a very broad overview of the suggested standards
here).
But, given that the US still uses ES for many business applications (e.g. liquid volume of beverages, although SI units are also listed), in much of the media and sports (e.g. "10-yard line"), and in day-to-day practice (e.g. I'm 5' 10" tall), I don't think that much more than the basic structure of IS sticks in kids' minds, at best.
However SI is used extensively in many high school and college courses (at least in the sciences and mathematics), though we often continue to use ES in those courses, as well. For example, although I mostly used SI, I once had to answer a question in Differential Equations about "mass" using ES. I didn't even know what the units were for measuring mass in ES! I had to look it up (it's "slugs," by the way).
I agree that it would be much simpler to do away with ES and exclusively use SI. But that seems to be taking us a very long time...
Regards,
Dan