The Classical Investigation, conducted from 1921 to 1924 by the American Classical League, remains the largest study of the teaching and learning of Latin and Greek performed in US schools. The recommendations that emerged from the Classical Investigation placed less stress on the claims of mental discipline and more stress on the value of classical study for the improvement of study habits and of facility with other languages, especially English. Yet the Classical Investigation also called for a turn toward a disciplinary purity conducive to a cultural reality that demanded high rates of literacy in Latin, a reality that had passed two centuries earlier. The Classical Investigation can be understood as an attempt to co-opt progressive commitments to educational "science", as a manifestation of social efficiency-social control ideology, and an effort on the part of educational traditionalists to preserve Latin as a source of class status and identity. (Contains 71 footnotes.)