If you start to teach popular music to young and/or middle school-aged children, you'll find that there is a great deal of music they are not aware of. I find that a little frustrating, as kids these days have access to so much more music than we ever did as kids. (I was personally pretty dependent on MTV as a kid.) The problem is that many of them don't know where to start. Yes, kids need to know who Beethoven was, but they also need to be educated on The Beatles and Marvin Gaye. As time wears on, we cannot take kids' pop culture education for granted.
So yes, teaching Johnny Cash songs within the context of a school music (or language arts or history) program is perfectly reasonable and very likely necessary.
“I Walk the Line” - Johnny Cash
Intro: Released in 1956, “I Walk the Line” was the first Country Billboard #1 hit for Cash. He had worked his way into fame, having played with Elvis Presley, Jerry Lee Lewis, and Carl Perkins in Nashville. The song went on to sell over 2 million copies, be recorded for future albums, and become a signature song of Cash's and the title to his 2005 biopic. Having sold over 90 million records and being a lifelong cultural icon, Cash had massive crossover appeal and was inducted into the Country (1980), Rock and Roll (1992), and Gospel Halls of Fame. He was also awarded at the Kennedy Center Honors in 1996 and received the Presidential Medal of the Arts in 2001. He passed away in 2003.
Analysis: Cash wrote and recorded the song after he was married for the first time, and its lyrics reflect his intention to remain devoted in his marriage. The musical content of the song, however, reflects the struggle, as Cash changes keys four times throughout the song (despite the fact that the original recording clocks in at under three minutes). Upon listening attentively, Cash can be heard humming the tonic of each new key as he changes. The song is structured strophically, with the only feature resembling the chorus a two line motif - “Because you're mine / I walk the line”. Each repetition of this motif is preceded by a verse, and after each motif and an instrumental break, a new key appears.
Considerations for Teaching: Johnny Cash is both an important historical and cultural figure in the US, and despite his notorious inappropriate behavior and multiple stints in prison, this song contains no material considered to be offensive in the classroom. The lyrics reflect a man committed to his marriage, despite the musical message depicted. Not only does this song serve as a good example of multiple key changes and leads to examination of their effect, it could also spark cross-curricular discussion, connecting the musical features of the song to Cash's poetic and literary value.