A case study traces the evolution of "once-upon-a-time" in a child's classroom story writing, drawing upon data collected in a three-year study of writing development in an urban magnet school. The subject, Mitzi, is observed from kindergarten through second grade. The study assumes that stories are cultural discourse forms that serve multiple functions and that, to internalize those forms, children must transform them into tools that are functional within their own social worlds. It is also assumed that children's discourse forms and functions are in a dialectical relationship: the initially awkward forms children produce may have limited social meaning--but those forms may elicit social responses that imbue them with new functional possibilities and thus lead children to further grappling with forms. In brief, the story forms young children learn from others are not the end products, but the catalysts, of development. (Five figures and one table of data are included; 30 references are attached.) (Author/KEH)