Here are some ideas on integrating writing across the curriculum on p. 127.
Use shared writing to create informational texts based on content material your kids have studied or other knowledge they have.
Have students keep journals in content areas to explain their thinking, problem-solve, and document their observations.
In the primary grades, use current content area information to compose sentences to use with word work.
Help other students be more strategic, reflective readers: have them keep a notebook or journal ihn which they write predictions or summaries, copy quotations, make notes, and create charts.
I'm sure we can come up with even more to add to the list.