Inaudible syntactic markers are especially difficult to spell. This paper examines how 455 fourth graders spell silent French plural markers in a dictation with real and pseudowords after one year of formal French instruction (L2). The Generalized Linear Mixed Model analysis shows first that noun plural spelling (real and pseudo) is a strong predictor for verb and adjective plural spelling. Second, the performance on real verb plural is higher than the performance on real adjective plural. In contrast, the performance on pseudoadjective plural is higher than on pseudoverb plural. Our findings indicate the strong influence of semantics and frequency in instruction input on plural spelling: noun plural is semantically grounded, and nouns are most frequent in the curriculum. Verbs and verb plural are also frequent, and inflection is mostly taught by means of memorizing the verb inflection paradigm. Adjectives are taught least frequently. The findings are discussed in the context of French L2 instruction, as the extremely low results on adjectives and pseudoverbs seem to be a consequence of instruction methods.