The Language Development Project was a major initiative in national curriculum development, the first of its kind in language education in Australia. The study focuses on three major themes or constructs underlying Phase II of the project, its developmental phase, and explores their implications for national curriculum development in the Australian federal context and for English language education in Australian schools. As such it is essentially an exercise in construct evaluation, a formative approach to the evaluation of outcomes. The study analyses the development of three major constructs: the tripartite model of language education; the cooperative model of curriculum development; and the collaborative evaluation model, as they were exemplified in the experience of the project, examines their relationship to the wider context of practice, and explores their implications for the development of a practical framework for the English language curriculum, the resolution of ambiguities in the cooperative model of curriculum development, and the development of a reconstructed model for the formative evaluation of cooperative national programs.