How can I argue whether or not "She's Leaving Home" by John Lennon and Paul McCartney can be classified as a traditional ballad? I must consider both structure and content in making the argument, and break the poem down and support the argument with evidence from the text and knowledge of traditional ballad structure.
This is not a cut and dried question, I'm afraid. Scholars disagree (passionately) on what constitutes a True Traditional Ballad. The general consensus is that they are folk songs, and are orally transmitted. The original authors are usually unknown, lost in the annals of time. Of course, the traditional ballad tells a story--they tend to agree on point--such as histories, legends, fairy tales, fables, jokes, and outlaws and love stories.
The oral tradition part predates the age of recording, and because it was traditionally transmitted orally (and usually sung a capella, as most people couldn't afford instruments), the lyrics would evolve over time (rather like a generational game of "telephone"). These songs tended to have repetitive choruses, as well.
While "She's Leaving Home" tells a poignant story (drama is another characteristic of traditional ballads), it doesn't really fit the rest of the usual requirements of a traditional ballad. It is a ballad, of course, but traditional? I don't think so.