Pajama Diaries: Crappy comic confuses me

Last month this storyline ran in Terri Libenson's terrible comic:

Okay. WTF, right? Like, who doesn't know their kid can read? I'm always confused about shit like this because apparently having learned to read at age four makes me some sort of freak, but wouldn't they have been working on at least her letters with her at home? Isn't that what stereotypical white middle class parents do? Mine did. I mean, I wasn't even aware for the longest time that kids learned to read in school because when I was in kindergarten they sent me and Nicholas Kicklaus (I swear that was his name) out in to the hall to read books with older kids. HOW DO YOU NOT KNOW THAT YOUR CHILD CAN READ?! Pajama Diaries has definitely established how "busy" the mom in this comic is, but seriously. Also, unavailable as of yet online, but Sunday's PD included excuses for her to get out of sex with her husband. Nope, no stereotypes confirmed here.