Why does Lorde initially refuse to write her name with a black crayon like her teacher requests

She thought that crayons were only for writing on walls or scribbling in coloring books.

‘I can’t,’ I said, knowing full well that what you do with black crayons is scribble on the walls and get your backass beaten, or color around the edges of pictures, but not to write. To write, you needed a pencil. ‘I can’t,’ I said, terrified, and started to cry.