Writing is the highway to learning, processing, organizing, storing and retrieving information during the school years. Gaining command of the structures and functions of texts of different genres is one of the main goals of linguistic literacy in education. The texts that school-goers construct provide optimal hunting grounds for unveiling their linguistic abilities during the genre-specific construction of different text types. The current study examines the linguistic constructions typical of expository texts, characterized by argumentation or persuasion regarding social / conceptual issues, versus informative texts, describing factual (or less controversial) phenomena. This examination constitutes a window on Hebrew-speaking students’ developing writing abilities in elementary, middle and high school, compared with adults. Participants were 547 students and educated adults with post-high school education. Each participant wrote an informative text and an expository text, yielding a total of 1,094 texts. Three types of variables were examined: lexical, morpho-syntactic and syntactic. We found that complex lexicon and syntax in discourse increased in prevalence across the school years, with specific structures being genre-typical as befits the stance and character of the two genres under investigation. We also found that it was only in adulthood that all of these components were employed in optimal fashion, at the culmination of the period of Later Language Development. Our results imply that informative and expository texts are indeed distinct in their characteristics, and that it takes many years of internal linguistic and cognitive development, on the one hand, and schooling instruction and experience, on the other hand, to achieve qualitative academic writing in non-experts.