The joke in today’s strip appeared in Sumerian cuneiform. It likely dates back even further in oral tradition, as seen in the following paleontologist reconstruction:

Of course back then, the trilobite’s twin didn’t step all over the punchline like Emily is doing today. And this “teachers are great” business? Hoy, Centerville schools must be in shambles.
Is Nate worried as all get out about what these two think of the school or what? Students moving TO Westview really is the rarest of rare cases, I guess, and he really is terrified of losing them. I don’t think Emily and Amelia’s mother cares half as much about their first day of school as Nate seems to.