I expect my students to include a beginning, middle, and an end to their stories. The beginning should include a hook (a sentence to grab the reader's attention), the topic sentence, and then answer the 5 w's (who, what, when, where, and why). The beginning should then end with a feeling sentence about the topic.
The middle is for supporting the topic sentence with main ideas and supporting details. Each main idea should be written into a main idea sentence beginning with a transition word. Then students need three good supporting details for each main idea. If students are having trouble with their supporting details, encourage them to think about the 5 w's again. They make great supporting details. I then teach the students to give examples of each supporting details. (I learned this from Four Square Writing.) After students give an example of the detail, they can then elaborate on the example. Judy Gould does a great job of explaining this and giving examples of how this works in her book Writing Workouts that Work.
Since students are writing three main ideas, the middle of their stories becomes three distinct paragraphs.
The final paragraph of course begins with a transition word and then restating the topic sentence. I then have my students either state the main ideas again or give an interesting idea about the topic. The ending should then leave the reader thinking. In my Super Writing Pack I put together, I made a poster of different types of endings students could use in their writing. Visit my TpT store or my Teacher's Notebook store to see more of my Super Writing Pack.