"School Spirit" and Football

Apparently the boom years of the 1920's also saw a boom in discussions of "school spirit", according to this Google ngram search.. I'm not sure what's going on there.  Maybe it reflects the "high school movement" described in wikipedia:

The high school movement is a term used in educational history literature to describe the era from 1910 to 1940 during which secondary schools sprouted across the United States. During this early part of the 20th century, American youth entered high schools at a rapid rate, mainly due to the building of new schools, and acquired skills "for life" rather than "for college." In 1910 less than 20% of 15- to 18-year-olds were enrolled in a high school; less than 10% of all American 18-year-olds graduated. By 1940, 73% of American youths were enrolled in high school and the median American youth had a high school diploma.^[1] The movement began in New England but quickly spread to the western states. According to Claudia Goldin, the states that led in the U.S. high school movement (e.g. Iowa and Nebraska) had a cohesive, homogeneous population and were more affluent, with a broad middle-class group.^[2][3]