A quality technical education spans an entire childhood. You just don't scab it over with four years of college and get the facility and perspective that is needed, building those dendritic connections while the brain is still at its most plastic developmental capability. Hence, when I home educated my daughters, they were doing college calculus by 12, self-taught.
“abysmal quality of K-12 teachers.”
One of my former neighbors here in Florida is a recently retired teacher. She and the instruction she provided were excellent.
“there is insufficient breadth and regenerative capacity to carry an economy primarily because of the abysmal quality of K-12 teachers.”
Any person who thinks that is ignorant. My father employed hundreds of people. I was sent to a public school because my father considered the ability to judge people accurately was the most important skill one could have.