For students to write effective paragraphs, they must first understand the function a paragraph serves in a larger story or article. By the time most students finish elementary school, they have a firm grasp on the elements that make up a story. Use these same principles to explain the structure of a paragraph. Present the class with a well-known story with a well-defined beginning, middle and end and map out the elements on the board. Read out a well-structured paragraph and map out that passage's beginning, middle and end next to the map of the story structure. Students will recognize that the paragraph structure mimics that of the larger story.
Once students understand the basic structure and purpose of a paragraph, they can begin to dissect the elements of a standard paragraph more closely. Write a simple paragraph on the board and ask the students to articulate out loud what the paragraph is about. They can then use that thought to identify the topic sentence, which highlights the paragraph's main idea. Circle that sentence in green to signify that it is the "go" sentence. Have the students identify the supporting sentences, which continue on that main idea. Circle those sentences in yellow. Help the students to identify the ending sentence, which essentially reiterates the topic sentence. This ending sentence should be circled in red, signifying that the paragraph's ideas have come to an end. Ask the students to write their own sentences and repeat the green, yellow and red identification process.
Even if a paragraph is structurally sound, it does not mean that it reads well. When students are in elementary school, their paragraphs usually consist of a series of choppy sentences that are not seamlessly linked together. By the time students reach middle school, they should be working on making their sentences flow together. Have the students come up with an object, an action and a place. Ask them to write sentences that include all three things. Have them reword a sentence, using the same three concepts, but written out in a different way. Instruct them to repeat this process a third time. This exercise teaches students how to vary their sentences. Once they have mastered this task, assign them to write a paragraph that exhibits this sense of variety. The paragraphs may seem awkward at first, but eventually the students will find ways to link their varying sentences in a way that flows well.
Since a paragraph is by definition part of a larger work, the ultimate goal is for students to use paragraphs to build a more substantial story or essay. Using the skills that they have built in previous lessons, ask students to write an essay or creative work consisting of four or five paragraphs. Assign them to write a mock newspaper article, a book report or a short work of fiction. As a class, examine the transitions between the paragraphs in the students' work. Ask the students if the paragraphs transition smoothly and help the students polish the transitions until the paragraphs work together to form a cohesive piece of writing.