One of a number of reports of a study of the writing development of 14- to 16-year-old students, this booklet is divided into two parts. The first part uses five criteria to analyze what four secondary students learn from composing imaginary stories: (1) What resources are used in the setting or situation? (2) What kind of ordering is used? (3) What is the significance in the point of view? (4) What sort of readers does the writer assume? and (5) What actual or potential understanding of the uses of language could be pointed to as being significant? These criteria are then discussed as they apply to four stages of writing development, ranging from an oral model to a more mature literary model, and as they could be useful in clarifying the kinds of achievements teachers respond to as they read student compositions. The second part of the booklet, using two specific imaginary stories as examples, suggests that teachers can offer students prewriting assistance in assembling imaginative resources and making rhetorical choices, and postwriting or revising assistance in diagnosing causes of partial success or failure and suggesting effective strategies for improvement based on the student's stage of writing development. (AEA)