We're apparently going to establish the fact that John and Mike don't have much of a relationship this week. We start, however, with Mike talking about Lawrence's cast.
Panel 1: We start out with John sitting on his recliner holding the day's edition of the Toronto Squiggly Line; he looks to his right and tells Mike, who's leaning on the armrest, "So, I hear Lawrence got his cast off today."
Panel 2: As John tries reading the headlines with his eyes shut, Mike says "Yeah. We wanted him to bring it in for show an'tell."
Panel 3: He goes on to say that Lawrence says his leg feels funny but he can walk fine.
Panel 4: The fact that Mike obviously feels sympathetic because Lawrence won't be able to kick anyone for a while makes John get gobsmacked.
Summary: I have no real idea why it is that Lynn thinks that little boys act like a bunch of cage fighters; sure, Aaron might have been a handful but she can't generalize like that. About the only way this does make real sense is if you assume that the other parents didn't want the dentist's crazy-ass wife near their kids lest their private lives end up splashed all over the funny papers.