Funny thing is, I don't exactly disagree with that perspective, either. Unified standards have their advantages, but they also play into the trend of framing education as a standardized commodity, with students as consumers, rather than learners. You see this often with the arguments that curricula must be uniform, so that the US does not "fall behind" relative to other countries, or become less "competitive." Unified standards also run the risk of promoting cultural obliteration, since schools are inherently institutions of acculturation as well as education.
It's tricky, particularly when it comes to Southern states, because since the Civil War, the relationships among the several regions of this country have only nominally been that of equals. Functionally, the Northeastern establishment has had hegemonic control over the rest of the country, while the "flyover" states have operated more like colonies. (Unfortunately, when the tables are turned, a certain vengeful and paranoid malice arises in government. Wilson and Bush the Second are good examples of this). Incidentally, that's one of the biggest divides behind the Red State-Blue State distinction: the states oriented toward trade and manufacturing on one side, the resource-extraction and agricultural states on the other. The former exercised power through the dollar - the New York banks financed the Midwestern factories and coastal exchanges, while the resource-extraction/agricultural states remained dependent on them to buy their products, making them somewhat subservient.
So, there's an understandable resistance to collective action by these states, assuming that the greater institutional power of those commercially-oriented "blue states" would allow them to dictate the terms of that action, possibly leading to cultural marginalization. It has to be unsettling to some that someone like me, who grew up just outside of Houston, speaks with an accent that is indistinguishable from that of a person from the middle of Ohio.