When she was in eighth grade, a Chinese friend of mine moved from Shanghai to upstate New York. (Her dad worked for General Electric.) In New York, she discovered she’d already learned eighth-grade math — in fourth grade. Her new school moved her to tenth grade math. It was still material she’d already had, but less absurdly easy.
If 80% of American parents knew this, would they abide it? Or would they decide that something is terribly wrong? Now, of course, almost no American parent knows this.