Which kids?
Which music?
Music overall?
I know more than most kids; less about some topics. I know kids who have more music theory under their belt than me, and most certainly know more about "their music" than I do. On the other hand, there's also great resistance on the part of many to know anything about "not-their music", as though ignorance of something signaled purity. It often goes hand-in-hand with a general "if I don't know how I'll need this and how it'll make me money or make me important, screw it" attitude.
One student was stunned that music without words even existed. "How do you sing along? How do you listen to it? What could it even be saying?" She apparently never heard of humming. She's 17. She sees no point in making music because she can just download it. Sadly, that's true for nearly everything else in her life ... I'm sorry, "life". She's the nearly perfect consumer.
There's also simple longevity at play. I heard Bay City Rollers music playing at some pizza place (yeah, Bay City Rollers, go figure) and knew who they were, etc., not because I'm especially fascinated by them, that genre, that period, or that part of the globe, but simply because I was alive and listening to top-40 radio when they did that thing they did.
Some is attitude to knowing things that don't mark my identity or reinforce my in-group status. I know '50s music because my mother had records that I played when I was young. I know '30s and '40s music because a friend's grandmother would play the music for us when I was a kid. It was okay to listen to "not my music" back then. Some is passive, but most is just curiosity. "Gee, she likes that music, I wonder what she sees in it? I know, I'll try to understand it."
I'd probably do okay with a video quiz that covered the 1600s, 1700s, 1800s, and 1900s. Not so big with CW and rap/hip-hop, though, and I'm weak on big band and swing. And most non-US/non-European musics. (I'll put what's written for guitar in 'European," even if it's Afro-Brazilian or Afro-Cuban.)
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). That was in the 80s and 90s that I was gathering up old blues CDs.