When did teenager start being an era? 1962, apparently.

In 1962 Paul Goodman published his book Compulsory Mis-Education. He wrote of the isolation of youth within the high schools (compulsory attendance in high school was still relatively new), where they were compelled to stay, day after day, excluded from interesting adult life and pressured to perform and conform primarily to keep them out of the adult job market and off the streets.

This forced isolation from the real world *created* a youth subculture which had formerly not existed, and which can be, like institutionalized school itself, viciously self-perpetuating.

Read more at The Common Room