What? A repertoire of practice refers to the sum of available tools, techniques, strategies, tactics, ways of working, expertise and know-how from which a practitioner may draw, choose from, and/or combine to suit both known and novel situations or address a particular purpose. The more expansive and well-developed a professional’s repertoire of practice the more likely they are to be able to respond appropriately and effectively to the challenges thrown up by practice and working with people with diverse interests, dispositions and backgrounds. Crucially the notion of a repertoire of practice, in the context of Learning by Design, is that it is open-ended, grounded in both experience and theory, developing fully only via discussion, dialogue and critique and as a result of iterative and repeated application, reflection, design and redesign.
A repertoire of practice develops via the practice which it makes possible.
Why? An expansive and expanding repertoire of practice provides the foundation for sophisticated professional endeavour and professional connoisseurship – it provides for deliberate and thoughtful choices between Knowledge Processes and pedagogical tools and the matching of these to learner needs and disciplinary contexts.
Ashby’s Law of Requisite Variety  says that ‘variety absorbs variety, defines the minimum number of states necessary for a controller to control a system of a given number of states. For example, the number of bits necessary in a digital computer to produce a required description or model.’
It follows that the more complex a system the more complex the ‘inputs’ to that system need to be in order to influence how it functions how it creates outputs, and by extension how it sustains itself. Classrooms with students from diverse backgrounds and with eclectic lifeworld interests and educational needs demand teachers with an extensive range of pedagogical skills and access to a broad range of tools and processes and the know-how to deploy and use those tools effectively.
Learning by Design is a means of expanding one’s repertoire of practice – it is not about right or wrong but deciding which Knowledge Processes to deploy, using what tools or tactics, in which circumstances for what purposes. Learning by Design works to expand the choices and pedagogical responses available to teachers so that there is an appropriate and effective response for every circumstance and student.