Learning to compose texts adequate for different purposes is crucial for becoming literate. We examined developmental changes in the rhetorical structure of written texts produced by Spanish children throughout the early years of elementary school in the light of descriptive writing purposes. Children had also performed tasks to test transcription, reading, cognitive skills, oral vocabulary, and discourse structure. Cross-sectional and longitudinal results show that the structure of the texts evolves from describing qualities to building a descriptive schema in which the described entity is introduced, qualities are justified, and a generalization is drawn from previously provided details. The ability to produce a self-sustained discourse, the ability to handle meaning relation among words, and a good working memory explained differences at a base level, whereas a higher command of spelling explained developmental changes in the structure of the text.