It is one of the simplest ideas in American education—and one of the most confounding: Elected officials and educators have been talking about establishing national, or common, academic standards for at least a half-century.

On its face, the logic of that goal seems incontrovertible.

Why should students in one state be introduced to a topic such as fractions as 1st graders, to cite a common example, when their peers in other states won’t cover that mathematics topic until later? More broadly, why does the United States—a mobile society in a globally competitive era—maintain an education system that tests students, trains teachers, and churns out textbooks and classroom materials based on the myriad and often idiosyncratic demands of different states?

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