In the present study, children who have been diagnosed as affected by specific language impairment in preschool years have been followed in the early stages of written language acquisition (first and second grade). The children have been divided in two groups, according to the level attained in language development at the beginning of first grade: one group had resolved the language problem, while the other still showed persistent problems mostly in phonological and morphosyntactic production. The two groups differed in terms of written languages abilities at the end of first and of second grade. The group with good language recovery showed an initial delay in reading and writing in first grade, accompanied by a delay in phonological working memory and metaphonological abilities, but reached a normal reading and writing level at the end of second grade. The group with persistent language deficits had also impaired phonological working memory and a metaphonological disorder and the proficiency in reading and writing was still very low at the end of second grade, compared to normal controls. The results support the view that the integrity of language based coding processes in phonological working memory and metaphonological abilities is a central factor for learning to read and write in a critical period.