This might sound a little far fetched but there was an Anything Muppet skit from possibly the mid/late 70's or early 80's that took place in the same classroom that went from being used for the "Roosevelt Franklin Elementary School" sketches and then used again for "That's What Reading's All About" (or "Sound it Out"...whichever it's called) and "My Rock". In it, a group of AM kids enter the classroom, and are amazed by their surroundings (from the blackboard, supplies, desks, the alphabet above, etc.) They then try to figure out what it is, obviously leading to different opinions (but not a big argument). Ultimately they decide to get to work, and resume their guessing later. So, they open up the top of their desks and once again start marveling over everything they see inside. But then they notice each desk has 2 letters on the tops ("SC" on the first, "HO" on the second, and "OL" on the third), and of course realize that they're in a SCHOOL...end of skit!
I used to have it as part of #3277, but my youngest sister accidentally taped over it back in late September 2007, so of course my evidence of this skit is gone...and unfortunately that was before I started getting into the tape trading game. But I can assure that I'm NOT making this up. Hopefully one day, SW will pull it out of the vault. Though, if anyone reading knows what I'm talking about, please let me know!