Prior to the early 20th century, there was no real social category of 'youth' and no semblance of a 'national youth culture' that Bailey discusses in the book. Young people quickly went to work and sometimes married early but largely spent most of their time with people in their community who often were not their age. Limited mobility meant that community was more important and generation unimportant. But with the rise of national media, like movies, magazines, and the radio, the increasing presence of national public schools and the generational linking that occurred as the result of World War I a gradual national youth culture came into being. In school, children were segregated according to age and spent most of their days separated from their elders. As a result, they spent most of their time with those of their age group and so a sharp cultural division between parents and children arose.