This is going to be complex. In my mind, it seems entirely appropriate for children to be taught that writing is risk taking. The best of writers are ones that take risk in their work. The composition of writing and its craft can only be enhanced through risk taking. Being able to instruct students as to how this is done in any many forums possible such as with word choice, unusual topics, or vivid imagery is intrinsic to good writing.
I think that the challenge comes with external and summative assessment of writing. For example, when students write for a state exam or some type of high stakes standardized assessment that examines their writing, the grading mechanism and rubric might not reward risk taking. It might even take away from the student's overall score if they employ compositional risk in a setting that might value or stress conservatism in writing. For example, recent advances in Common Core Close Reading/ Writing features greater emphasis on what students can prove through textual analysis, as opposed to the use of rhetorical questions and personalized narratives in answering prompts. This is a challenge that all teachers face when teaching students in light of school districts having to be assessed and teachers being burdened with the reality of external, summative assessments.
With this in mind, I feel that we do our students greater service if we teach them that writing is a risk, in general. There are times when we must write with our audience in mind. In a setting where a rubric to assess student work is not one that automatically rewards compositional risk, students might have to be more conservative in their approach. In a setting where rubrics and metrics to define student success are more rooted in compositional risk, students can take those risks. Overall, good writing is good writing. Yet, I feel that it is important to teach students that there are realms in which the writing process is pliable enough to recognize when risks can be taken, and where risk has to be balanced with the audience in mind. In order for our students to be able to become writers that will transform our understanding of writing, they have to be taught what that spectrum is. In being able to understand this spectrum to its fullest extent, students can possess the tools needed to succeed in it and then, if they choose to do so, transform it. In this, one sees where the power of instruction in risk taking, in general, becomes evident.