Many times thruout a school day, students end up having "free" time cos of perhaps they have finished their assignments early, "have nothing to do", there work needs to wait for something before they can go foreward, etc. I've found that many students do not use their free time in a productive way so I assign those students a writing assignment.
Whatever the reason, writing can always fill up the slack in a classroom day. Students can write with pencil and paper for extra credit or just to express themselves. Writing in of itself promotes penmanship, grammar, spelling, reading, motor skills etc.
The problem I find that most students in doing this assignment is subject material - what should I write about. It seems to be a major obstacle to students to choose something about which to write. So I bring to class a list of topics that act as prompts that involve everyday life from which they can choose to write. with pencil and paper. this is not a computer based assignment.
They may choose to get an extra credit grade or no grade at all but they do have to turn their writing in because it does get corrected. The writing gets handed back as well so interested students can see where they can improve.
Students are simply given a page or two of lined paper and asked to write at least five pargraphs about whatever topic they have chosen. They may begin with an outline that the teacher reviews before actual writing begins. A title is mandatory. If they finish their writing before the class is over, then they may go on to a second topic.