The bureaucratic mind at work:
The US presents particular obstacles to achieving educational improvement at a national scale, deriving from its social and economic diversity and also from an entrenched tradition of “local control,” which precludes a federal role in any primary initiatives. Yet to achieve effective reform at scale requires some national coherence. This was a principal aim of the Common Core, embodied in the word “Common.” Fractions are the same in Florida and Montana; it makes little sense in a highly mobile population for the math curriculum to change at state lines. It would be like building a national railway system with different gauge tracks in each state.
When everybody is learning the same stuff, everybody will be making the same mistakes. When there are many different education plans, even people who are miseducated can learn the truth from others after graduation. When there's just one plan, there are very few such others and those that do exist will sound like (and sometimes be) crackpots.