In the historiography on curriculum reform during the progressive era, one interpretive lens has dominated the study of 20th-century reform for more than 40 years: the idea of the "social efficiency" doctrine. In this historiographical essay, the authors briefly trace the rise of social efficiency as an idea in curriculum history, identify the four common assertions on which it is based, review the recent studies that challenge these assertions, and finally, suggest some ways to rescue the term from overuse and abuse. The authors argue that, historically speaking, "social efficiency" was a widely used, poorly defined, highly problematic term that had multiple uses for multiple scholars between the 1890s and the 1930s. Historiographically speaking, the authors argue the idea of the social efficiency doctrine has been an inconsistent, heterogeneous, and imprecise lens through which to explain long-term curriculum change.