This communication examines the dynamic development of word identification and narrative comprehension abilities in reading among first-grade French-speaking students. Based on data collected in France and Quebec, in the middle and end of the first year of schooling, this analysis highlights a threshold effect in the relationship between word identification ability and reading comprehension. Below this threshold, which changes little between mid-year and the end of the year, reading comprehension is almost entirely determined by the fluency of word reading, whereas above it, the weight of word identification in explaining reading comprehension abilities decreases significantly.