This research aims at exploring in an irregular orthographic system like French, if spelling is related to written composition. French spelling is particularly interesting because it includes phonographic irregularities (i.e., inconsistencies), lexical difficulties and numerous morphological silent marks (e.g., plural noun, adjective, and verb agreement). In a longitudinal study from the beginning of Grade 3 to the end of Grade 4, pupils (N = 173) were asked twice in every grade to compose narrative texts from strips. Text length, text completeness and three categories of spelling errors were coded and analyzed through multilevel growth curve models. Results show (1) a growing relationship between text production and orthographic performance, (2) that this relationship varied according to whether it related to text length or to text completeness, and (3) its strength and evolution depended on the type of errors (phonographic, lexical, or morphological).