The linguistic demands of poetry writing, quite apart from the transcriptional aspects of writing, make this perhaps the most challenging form of writing children encounter in school. These would include, among others, poetic techniques such as using line breaks and chunking meaning in stanzas; invention and handling of imagery; playfulness and ambition in vocabulary. In this paper I want to examine some of the linguistic and cognitive demands which writing poems makes on children. I will analyse these using Sharples' model of thinking about writing, specifically his description of "rhetorical and content modes"; and I will argue that poetry writing makes unique demands upon children in both of these modes. I will critically examine how the content and rhetorical modes can be expanded through the use of published poems as literary forms, and will discuss the potentials and pitfalls of this approach.