At any rate, GP is right that it's not the "growing middle class" in China that sends kids to private school in the US. It's the upper class.

Make it about half a million Chinese students in the US currently, so we're talking about the top 1%.

If they were defined by percentiles (i.e. certain definitions of middle class dictate the middle 60% of the population by income), you could still describe a "growing middle class" as a middle class acquiring a greater percentage of total income. While the population of the middle class isn't growing, its buying power still could be.

Well sure, but that's not what anyone means by those words.