I'm paraphrasing here--but I can't imagine we don't know this: the genres we have students practice in our writing courses has very little to do with the kinds of writing they do after they get out of school.
Norbert and his colleagues surveyed (and I'm going from memory here) secondary, post-secondary, and post-graduates to evaluate alignment on what we teach and post-pedagogical transfer. From transfer and genre theory, we know that transfer links to genre-similarity. This should be no surprise. If we teach students how to write 5-paragraph essays, their clunky knowledge about writing will not make them poets.
Norbert and his colleagues found that postgraduate writing is not what we teach--in other words, limited transfer. Seven percent of postgraduate writing (surprisingly high) resembles the "essay."
We should think about this disjuncture between what we teach and the utility of what we teach--and certainly about the referentiality of reproducing ourselves through what we teach.
I can imagine where this line of inquiry would lead--theories of social reproduction, social class and ethnic discrimination, mindless pedagogy, teachers unaware of how they are cogs in the machine. In this post, I'm only going to suggest these implications--my real thesis being that we are too easily inculcated in a project of teaching students how not to write by imagining that we are teaching them how to write.
I had better stop here. But I wondered what Norbert et al.'s data would have shown if they had investigated the frequency of non-academic and non-professional writing that people do--for me, the kind of writing that matters.