Education introduces learners to the social practices of communities. A social practice is a unit of culture which involves knowledge and action in a theory/practice relation. Knowledge structures (KSs) are meaning patterns of the discourse, knowledge and action of a social practice. In our 'Knowledge Framework' model, the typical KSs of a social practice include at a general theory level, classification, principles and values, and at a specific practice level,

description, sequence and choice (Mohan 1986;Mohan, Leung & Davison 2001, Mohan, in press).