One graphic illustration of the way a paragraph is structured is a hamburger. The top bun is the opening sentence, the bottom bun the ending sentence. In between you put your supporting details — the meat, lettuce, ketchup and other ingredients. Without the buns, the hamburger falls apart, but without the supporting details it’s not very interesting. For a tasty snack version, use vanilla wafers to represent buns, a peppermint to represent the patty and various colors of icing or shredded coconut for vegetables and condiments.
To help your students understand for themselves what the point of a paragraph is within an essay, read together through one or two essays of five or six paragraphs each. When you are sure that they understand the essay, focus on one paragraph within it. Ask them questions about how the topic of that paragraph pertains to the topic of the essay. Move on to the next paragraph, helping them to see that each paragraph, while self-contained, is a part of the larger whole of the essay.
After your students understand how one paragraph fits within a larger essay, focus on the structure of the paragraph itself. Look at various paragraphs, pointing out together the introductory sentence, the way that the following sentences explain the topic and how the last sentence finishes it. Try taking a sentence from somewhere else in the essay and asking them how it would sound if it was put in the middle of that paragraph.
Ultimately there’s no better way to learn than by doing. Write a paragraph as a class. You decide the topic, then encourage the kids to contribute ideas and sentences until you have a completed paragraph. Repeat as many times as necessary, then ask students to write their own paragraphs. Review the paragraphs with them, pointing out when they get their sentences out of order or if they include information that doesn’t relate to the topic.