This post will need a little preface so you can appreciate the humor more. The 'ch' in the story has a ches sound.
ZB (5) was learning letter 'S' last week and the teacher expanded on the the letter by teaching the kids about spiders.
ZB: Ema, I learned about arachnitz (ches sound) today.
ME: What's that?
ZB: spiders are arachnitz not insects
ME: Do you mean arachnids?