Here is Cultural Literacy worksheet on the topic sentence as a unit of composition in a paragraph. This is a half-page document with a reading of two sentences and two comprehension questions. A basic, symmetrical, and surprisingly thorough exposition of the form and function of a topic sentence.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.