Panel 2: Okay, is that supposed to be funny, that the kid brought in a whole branch? Meanwhile, I'm reminded of a Peanuts strip in which Sally brought in a leaf for show and tell, remarked, "You will notice, of course, that I left the tree where it was!", busted a gut laughing at her own "joke", then, after presumably being reprimanded, said briskly, "Okay, now about this leaf." Lynn is no Charles M. Schulz, that's for sure. When Peanuts characters tried to be funny and weren't (which was deliberate), the humor was in seeing their effort go over like a lead balloon. There was no need for a sticky-outy tongue basically ordering the reader to laugh along with the joking character.
Panel 3: :::Cookie faints from surprise::: John did something for Liz? What, was he channeling his frustration at being abandoned by April?
Panels 4-5-6: Well, that is interesting. Seriously, I actually learned something here! And I like how it's a red maple leaf...what else? However, that is a bizarre angle on Liz in panel 6.
Panel 7: "Shtaa-taa-haa"? Is that supposed to be laughter?
Panel 8: Oh for crimeny sakes. If I were Liz, I would be pissed. However, I wonder: how long did it take for the cheese sandwich to find its way in to the leaf press? (And was "shtaa-taa-haa" the sound of it being squished? In fact, if it is, that would explain Liz's expression in the previous panel.) I'm genuinely confused, because I do remember a few instances of sabotage when I was in elementary school, but they generally took time to develop. This almost seemed like the kids had the sandwich ready ahead of time. So is the message here that you can't take your eyes off these kids for five seconds before they wreck something? And I don't even see Jesse in this strip, so what's up with that?