If it's in writing, it must be true

Zoey was upset on Friday after she came home from school. She said that some boys in her class said she was not a good artist. "Why would they say I am not a good artist?" she asked me. I tell her, "Don't worry about what they say, you know that you are a good artist. And mommy and daddy think you are very good!" She made a face, clearly not satisfied with the answer, and then all of a sudden, an epiphany! "Oh!" she exclaims, "They said that, because they didn't know." And she runs off. And then she asks me how to spell the words good and artist. I am now quite intrigued about the solution she has come up with. She walks up to me with a paper taped to her shirt, like a name tag. The paper says,

Zoey
The Good Artist

"There, now they know. They just didn't read the sign."