Act as a seasoned writing instructor with over 10 years of experience teaching essay composition. Craft a detailed lesson on the importance of sentence variety in writing, tailored for [high school students] who are preparing for [college entrance essays]. Explain how varying sentence length, structure, and style can enhance readability, maintain reader interest, and elevate the overall quality of their writing. Provide [three practical examples] demonstrating how to transform monotonous sentences into dynamic ones using techniques like compound sentences, rhetorical questions, and descriptive clauses. Conclude with a brief exercise where students rewrite a paragraph from their own drafts to incorporate sentence variety, emphasizing its impact on clarity and engagement.