"The reason performance hasn't improed has nothing to do with IQ and everything to do with a dumbed-down or useless curriculum."
I agree. Given the right kind of instruction, the vast majority of people, including those with "below-average" IQ (an ill-defined concept at best) can learn to read, write, and do arithmetic and probably some simple algebra (percentages, ratios, fractions, etc). Our schools have failed a significant percentage of our students in transmitting even those basic skills. No, not everyone is university material, or maybe even academic high school level, but there's absolutely no excuse for our schools turning out students who are functionally illiterate and innumerate.
You get it.
The more amazing thing is that most people can even teach themselves anything they want to learn without formal schooling - once the basics are learned.
And that's the kicker. We're creating entire generations of helpless, dependent people who cannot think for themselves.
They can't even teach themselves anything because they have been brainwashed into thinking if they learn it outside of school it's not valid learning. There is a pervasive belief that if you aren't taught by someone with a license, then you have not learned the subject.