My Ramblings About Writing ...
For over 20 years I have worked with students on writing and a common thread seems to surface ... What do I write about? As adults, we have many years of experience to draw from but kids have very little. They just haven't been around that long. You, as a teacher, must begin to pull from them what they know. Find out their interests, hobbies, the weird relatives they have, a memory, a fear, or what they want to do in life. Read to them and discuss some of the books in depth. Point out descriptive words, phrasing, ideas, and how a book is tied together. Ask questions about plot, characters, setting, mood, voice, intended audience, point of view, theme, and any other elements of writing. These aspects of writing then become second nature to them.
Go for a walk. Observe. Take notes. Share discoveries. Bring old, dirty boots into your classroom and see what types of stories they can come up with. Hang items upside down from the ceiling after school and the next day, without explanation, let them decide what happened. The more obscure the items, the more interesting the imagination. Do anything that will add to what they already know.
Check out the books I've listed under the Teachers tab. They're good for getting kids to think, record, and write. Start out easy and short. I like to begin with journaling and descriptive paragraphs. They're easier to write than a story, easier to discuss, and easier to rewrite.
My best student writing happened when I gave them lots of time to write. It's probably the greatest gift you could give them. I know how much time I put into my writing and then we ask our students to produce something good in half an hour. Let them write!
There's really no magic formula. Just hard work, discussion, and enthusiasm on your part. They will follow your lead.