Hinkel (2013) draws a distinction between spoken grammar and written academic English in terms of teacher workload and learning burden (p. 4). On one hand, written academic discourse sets a considerably high standard for accuracy and precision of expression, and consequently, requires greater effort on the part of instructors and students to meet those standards. On the other hand, spoken discourse – while also requiring a certain level of accuracy – may be less demanding and “more fun” (p. 4).
A number of factors may account for this disparity in written and spoken discourse. For example, spoken language requires online (real-time) processing, which is fraught with errors, disfluencies, and revisions. Every speaker is constrained in his or her production by the limitations in cognitive resources, including context, body language, and other suprasegmentals, to aid us in getting our message across – not to mention immediate feedback from our listeners.
Written academic language doesn’t impose the same demands as immediate, real time expression; however, the demands come in the form of deliberated, cogent argumentation of more complex and abstract ideas. Written academic discourse is often considerably more content-rich than spoken language and strives toward different goals – exchange of knowledge versus negotiation of social relationships.
These distinctions are important for students because they must be aware of the relationship between context and communicative goals to make linguistic choices that produce their desired effect. If they want to participate effectively in academic discourse, they have to know the conventions of that discourse community and have the language skills in place to communicate optimally in that context.
I don’t think there is one time in particular to address such differences; I think an emphasis on register should be a feature of every grammar lesson. I would take a more functional approach to grammar instruction including a syllabus organized around communicative goals that explores a range of linguistic choices and their illocutionary and perlocutionary effects.