"What better environment is waiting outside of the nuclear family for children in not-so-great families? One barometer is how many foster families are available for troubled or special-needs children. I think the supply of high-quality situations is severely limited."
Of course the supply is limited, when those best suited to fill this need are (at best) strongly discouraged from getting involved.
"schools could be vastly improved. Lots more money would help"
LMAO. Quadrupling funding has been accompanied by a degradation of education. What makes you think even more money would make anything better?
As for driving - automobiles ended up raising the age at which children became independent, for the reason you mention of deadly accidents. My grandmother was driving at age 10, but it wasn't an automobile. In her day, children had a lot more independence than they do now, but it was coupled with social norms that required responsibility. With self-driving automobiles and other modern technologies, perhaps those days will return.