Fitting in writing instruction can be tricky enough, but getting students to write throughout the day can seem like a true challenge. Responding in writing, journaling, answering open-ended questions, and quick writes are all little ways to tuck writing in throughout subjects. Science and social studies are often taught through literacy, and so the writing connection is easier to see. Math seems to get the short end of the stick, yet writing to explain can be powerful for kids of any age.
https://www.scholastic.com/teachers/blog-posts/meghan-everette/2017/Graphing-and-Writing-When-ELA-and-Math-Collide/