Early-twentieth-century Progressives wanted to excise the “cancer” of child labor in part because they thought that adolescents should be in classrooms, not at work. As Philander Claxton, U.S. Commissioner of Education, explained, “We cannot educate children … for a democratic government in an age like ours, if we have them in school only through the years of childhood and previous to adolescence.”

The nineteenth century's common school movement advocated public education of children. Twentieth-century education policy required that adolescents attend high school, transforming an institution previously meant for a tiny elite. Less than 7 percent of all seventeen-year-olds in the country were high school graduates in 1900. By 1940, almost half were. The percentages of American youth earning a high school degree steadily increased before stalling in the mid-1970s at a little over eight out of ten. That was a policy success, with unexpected consequences. Extended schooling changed the daily lives of a majority of adolescents. However, generations of educators and politicians debated how and what to teach the millions of kids now forced to stay in school for most of their childhoods. In 1923, analysts at the U.S. Office of Education concluded wearily that much of the time they were “laying down principles in the dark.” That continued to be true throughout the century.

Nonetheless, acceptance of the idea that a prolonged period of education should be mandatory was enormously important.