I think the simple truth is that there's no free lunch. If we actually believe every child deserves an excellent education, we have to acknowledge it's going to take radical investment at the deepest levels of poverty, working upward from there. It's not impossible. Cuba sent teachers to every remote corner of their island to eradicate illiteracy, and largely succeeded. It's one of the few successes of the revolution.
We spend astronomical amounts of money incarcerating the more people per capita than anyone else in the world. Imagine if we applied that level of thoroughness to education.