This paper gives a brief summary of Halliday's theory of how children learn to talk, illustrating the development of children's language from the microfunctions through the macrofunctions and into the metafunctions of adult language. The paper points to a possible source of the misinterpretation of Halliday's theory in the work of Frank Smith (1983), which appears to have "trickled down" into some of the textbooks written for pre-service teachers in Australia. Links are made to teachers' knowledge about language (KAL) and the current Australian Curriculum English (ACE). It is suggested that while any number of functions of the language of school-aged children may be described, it is perhaps misleading to refer to the microfunctions as "Halliday's functions".