I run in to this problem all the time in my class. I assume something is general knowledge and I refer to it and then realize that the kids have no freakin' idea what I am talking about.
For example - Mad Libs were totally cool when I was a kid (I am 33). Everyone my age in town knew what they were. I did an activity in my class today and only 2 of my students had heard of them. Kinda blew my activity out of the water.
I had to ask my kids like 3 times to get out paper one day (not a normal problem but it was spring, the weather was nice and they were squirely). I say "Jeez guys, I sound like a broken record." They keep digging for paper and, when they were done I asked if anyone had an idea what "I sound like a broken record" meant. They had no clue but they made some good guesses. I had to explain what a record does when it skips.
What other things that we consider common knowledge won't our kids know?
***I teach a class of new immigrants and I now teach 9/11 in that history class. These kids were in 2nd grade living in a foreign country when that happened. They know what it was basically but politics and details are not something you pick up in 2nd grade. Crazy to think about.
Re: What our kids won't know...
As a sixth grade teacher, I had these moments often. They were very young for 9/11 as well and, while they knew a lot about it, it's so different than the classes I had just a few years ago that remembered exactly where they were and how they found out about it.
I have made numerous movie/song references that my students don't have a clue about.
My favorite was when a student came in singing "We will rock you" and then asked if I'd ever heard that song before ... she didn't realize how old it was!
Last year one of my students (she was 11) told me boss about this really cool machine that her mom had just inherited from her grandmother. You put these plates on it and it would spin around and make music.
After a few minutes, we realized that she was talking about a record player!
I know my SS played with Mad Libs because the freaking things drove me insane. I think he even had Sponge Bob ones! And he's only 14 (1994), so they're not that strange - maybe it's just because your kids are immigrants?
SS doesn't understand life without computers as a source of entertainment.