This investigation contributes to issues in the study of second language transmission by considering the well-documented historical case of Anglo-Norman. Within a few generations of the establishment of this variety, its phonology diverged sharply from that of continental French, yet core syntactic distinctions continued to be reliably transmitted. The dissociation of phonology from syntax transmission is related to the age of exposure to the language in the experience of ordinary users of the language. The input provided to children acquiring language in a naturalistic communicative setting, even though one of a school institution, enabled them to acquire target-like syntactic properties of the inherited variety. In addition, it allowed change to take place along the lines of transmission by incrementation. A linguistic environment combining the ‘here-and-now’ aspects of ordinary first language acquisition with the growing cognitive complexity of an educational meta-language appears to have been adequate for this variety to be transmitted as a viable entity that encoded the public life of England for centuries.