We propose to model the development of language by a series of formal grammars, accounting for the linguistic capacity of children at the very early stages of mastering language. This approach provides a testbed for evaluating theories of language acquisition, in particular with respect to the extent to which innate, language-specific mechanisms must be assumed. Specifically, we focus on a single child learning English and use the CHILDES corpus for actual performance data. We describe a set of grammars which account for this child’s utterances between the ages 1;8.02 and 2;0.30. The coverage of the grammars is carefully evaluated by extracting grammatical relations from induced structures and comparing them with manually annotated labels.