American public school districts numbered more than 200,000 in 1910. By 1970 there were fewer than 20,000. The decline was almost entirely accounted for by the consolidation of one-room, rural schools into larger school districts. Education leaders had long urged districts to consolidate, but local residents voted to do so, I argue, only after high school education became widespread. Graduates of one-room schools found it difficult to get into high school. Rural districts that were not "making the grade" were unattractive to home and farm buyers, and the threat of reduced property values induced voters to agree to consolidate.
Fischel, William A.
"Neither "Creatures of the State" nor "Accidents of Geography": The Creation of American Public School Districts in the Twentieth Century,"
University of Chicago Law Review: Vol. 77
, Article 8.
Available at: https://chicagounbound.uchicago.edu/uclrev/vol77/iss1/8