A Longitudinal Study of Writing Development in Lower Elementary School Students: Focusing on Productivity and Vocabulary in Descriptive and Expository Texts

Objectives: This study longitudinally examined the writing development of lower elementary school students by analyzing their descriptive (My mom) and expository (Making Gimbap) writing, with a focus on productivity and vocabulary. Methods: Longitudinal data were collected from an initial cohort of 23 first-grade students through three topic-writing tasks (narrative, descriptive, and expository) administered once a year under consistent conditions. While 23 students participated initially, the number decreased to 19 by the third year. This study analyzed data from 16 students who completed all three writing tasks. Building on a previous study of narrative texts (Bae, 2025), the present analysis focused on descriptive and expository writing. For writing productivity, variables including Terminal unit (T-unit), number of total words (NTW), mean length of T-unit in words (MLT-w), number of different words (NDW), type-token ratio (TTR), corrected type-token ratio (CTTR), and vocabulary density (VD) were examined across grades and text types. Vocabulary use was analyzed by identifying cross-grade common words (CWG), grade-specific words (SWG), and their semantic categories. Results: The productivity variables exhibited an upward trend across grade levels in both text types except for VD. Descriptive texts showed higher T-unit, NTW, and NDW values, whereas MLT-w and VD were greater in expository texts. CWG were related to the semantic frames such as [ROLE], [FIGURE], [CHARACTER], [INGREDIENT], [COOKING METHOD], etc., while SWG showed how vocabulary and its semantic categories expanded across grade levels. Conclusion: These findings suggest that even lower-grade students adapt their writing style according to text type. CWG and SWG offer clinical implications for writing intervention, for instance, how to match semantic frameworks with appropriate words and how to select vocabulary suitable for each grade level.