In this paper, ‘child’ second language acquisition is defined as distinct from both ‘adult’ second language acquisition and from either monolingual or simultaneous bilingual development in childhood. It is argued that ‘second language acquisition’ begins at a very early age (certainly before age 3) and suggest that there is a gradual development of features that become recognised as ‘adult second language acquisition’ after approximately age 7. Using this definition, the paper explores both grammatical and pragmatic features of child second language development, observing how children behave in formal instructional settings where the ‘second’ language is either that of the surrounding community or of a distant community. It further explores what second language acquisition research can (not) teach us about second language instruction, especially the facilitating role that teachers can play in supporting child second language development.