To ensure adequate writing support for children, a profound understanding of the subskills of text quality is essential. Writing theories have already helped to better understand the contribution of different subskills to text quality, but empirical work is often limited to more general low-level transcription skills like handwriting fluency and spelling. Skills that are particularly important for composing a functional text, while theoretically seen as important, are only studied in isolation. This study combines subskills at different hierarchical levels of composition. Executive functions, handwriting fluency and spelling were modeled together with text-specific skills (lexically diverse and appropriate word usage and cohesion), text length and text quality in secondary school students' narratives. The results showed that executive functions, spelling and handwriting fluency had indirect effects on text quality, mediated by text-specific skills. Furthermore, the text-specific skills accounted for most of the explained variance in text quality over and above text length. Thus, it is clear from this study that, in addition to the frequently reported influence of transcription skills, it is text-specific skills that are most relevant for text quality.