If there's sufficient motivation for the private sector to invest, it should either be improving the current system or creating an alternate one. To my knowledge, it's not doing either. I suspect that the reason is that they simply aren't in a position to get together to invest in a long-term "commons."

As for the current system's performance being "miserable" and "falling," well, it's no secret that we disagree. On international tests, the US falls in the middle. Unacceptable, but not miserable. And I'm not sure that I see evidence of "falling." Treading water is a better representation.

I'm of course aware that you've argued that our current system is only operating at 1% of its potential, and that by that measure, you might say that even the best nations (Finland, Singapore, et.al.) are miserable. Possible, but I'm not aware of any measure by which we can say with any substance that public education worldwide is operating at 1% of its potential.