Why the five sentence paragraph? One reason is that teachers seem to think five sentences are long enough to explain a subtopic, but not too long. One or two sentences seem skimpy, while seven or eight sentences might seem unduly long. Five is just right.
But I think limiting students to five sentences straitjackets their writing. For example, I encourage students to use dialog to enliven their essay writing. But when they find out that each time the dialog shifts from one person to another a new paragraph is needed, they freak out. “But then I will have too many sentences. And too many paragraphs!”
Sometimes students think up an excellent example that cannot be neatly stated in four sentences to follow the topic sentence of a body paragraph. They tend to skip that example and settle on something less detailed and less good in order to limit their paragraph to five sentences.
When as a writing tutor I am working with students who know that their teacher demands five sentences per paragraph, I back off. But when I am working with students who are writing to improve their skills, I encourage breaking this lockstep format.
Next we will discuss transitions.