We report in this paper on one aspect of a project designed to support teachers with the demands of the Language strand of the Australian Curriculum for English as this guides their development of a coherent account of knowledge about language and their implementation of this in building their students' literacy repertoires. We map the changing orientations of two teachers across the transition years, as they build their personal understandings of language as a resource for meaning and translate this into curriculum and assessment practices designed to strengthen their students' written persuasion. Through this mapping, we identify professional achievements and remaining challenges for the sustainable development of a "grammatics good enough" for the work of devoted teachers, who, without the opportunity to re-train as linguists, seek to build and implement their knowledge about language at the chalkface. Finally, we identify challenges that remain for the sustainable building of both teacher "knowledge" and "know-how" to ensure the kind of continuity and cumulative learning about language required for student success in persuasive writing, both in the transition years and across the years of schooling.