The first big writing topic I had the students work on was describing function behavior. I gave them a picture of a piecewise graph and had them describe what was happening. They were required to include the domain, whether it was increasing, decreasing, or constant, and what type of function it was (linear and quadratic). They also needed to include whether or not there was an undefined domain on the graph.
At first, I said write a paragraph without much guidance, and I quickly learned they needed a few more manageable steps. I asked them to annotate their pictures first because that seemed doable to them. From there it was easy for them to form sentences because they already had their information in front of them.
Like anything, they needed some practice with this, but they began to figure it out and writing domains became more natural for them. The structure of their sentences could still use improvement, but I still have a lot of time to work with them.
The second writing task I gave my students went along with rational functions. The students had to figure out the places where the denominator would equal zero. Those places could either be a hole or an asymptote.
In their sentences, they needed to include whether it would be a hole or asymptote, where it would occur, and why. I gave them a sentence stem to help them structure their sentences correctly. One thing I've noticed is that they don't know why they are doing things or why certain things happen. Including the explanation portion has helped them solidify why something is a hole verses an asymptote.
Overall, my writing experiment has been really positive. They kids complain because they don't think they should have to write in math class, but the complaining has decreased as they have figured out that the writing is not going away.
I also shared some of these things with my cross-curricular group of teachers I meet with once every six weeks. One of them is a 9th grade English teacher, and she was very pleased that writing with explanation and support was happening in math classes. Some of the other teachers in the group want to include writing prompts in their classes too. I love that this very important need for writing practice is spreading.