A bildungsroman is a coming of age novel that is written about how change occurs over time starting off with a loss or tradgedy. While Hughes may have written some aspects of a bildungsroman, the poem itself is not one.
This poem is not a bildungsroman because it does not explain how he has changed over time. It only explains how he is colored and different from his instructor as well as the other students. For example, he says, “I am the only colored student