What is the only requirement the students must fulfill when working on their end of the year poem in the novel, The Year of Billy Miller?

Mrs. Silver tells her students that the poems can be in any form, but they must be about a family member or loved one. Emma chooses her grandmother, for example, while Billy chooses his mother. Billy attempts to memorize the poem for the show, even though it is not required. Though Billy is not successful, his poem is still a hit with the audience, and Billy’s mom especially loves the poem.