On Monday morning, I always have each child's Weekend Journal waiting at their table spot. At the beginning of the year there is a large amount of space for drawing and a smaller space for writing. As the year progresses, the space for drawing become extremely small and the writing area consumes most of the journal page.
This document includes the cover page and pages for each quarter, progressing in writing space as noted above.
I've found this to be a great way to get authentic samples of children's writing. It also is excellent for noting grammar, punctuation use, and handwriting.