(Original Publication Date, 4 September 1990)
Panel 1: We start things off with Liz telling John to "lookit" (Nagging Idiot Woman for "unproductive argument about enunciation") all of the new stuff she got for school. We await the arch, whining and ignorant Lynn's Comments that date her horribly by use of the phrase "In my day, they didn't call people who use the phrase 'in my day' old fossils long past their sell-by date" when school supplies turn out to be pens, pencils, an eraser (to gnaw on), safety scissors and a ruler instead of a horrible SCREEN with Facespace and YouSomething and other horrible things that Lynn fears.
Panel 2: We set up the joke by having her realize at the last second that she forgot to buy a new pencil case; John plays his part by telling her that she's good to go because she's already got one from last year.
Panel 3: She says that she could if it were any good. John asks why she thinks this.
Panel 4: When we see it covered in the doodles and scribbles that a bored child is going to deface something with and says that there's no more room left on it, John's baffled reaction hints at the second-most important word Elly ever says: structure.
Summary: There's a damned good reason why John isn't frowning in irritation at typical little kid behaviour: he has the same mental infirmity Elly and Lynn have. Elly uses a word that points out what that mental failing is on Friday.