Start your lesson by defining "compound sentence" and giving examples. Write the definition on the board and ask students to copy it into their notebooks. Remind students that an independent clause has both a subject and a predicate and expresses a complete thought. For example, two independent clauses are, "thunder rumbled" and, "the scared dog hid under the bed." When those two thoughts are combined with a comma and conjunction, we have a compound sentence: "Thunder rumbled, and the scared dog hid under the bed."
Write some common conjunctions on the board (for, and, nor, but, or, yet, so). Explain to students that the comma and conjunction are like the glue that combines two independent clauses. Then give students several pairs of independent clauses to practice combining with the conjunctions. You could write these on the board or print them on a handout.
Examples of independent clause pairs could be "I had a vanilla cupcake with sprinkles" and "it was delicious," "I had fun at the beach" and "I got sunburned," and "I'm tired" and "I'm going to bed early tonight." Ask students to volunteer their sentence combinations. The sentences should read, "I had a vanilla cupcake with sprinkles, and it was delicious," "I had fun at the beach, but I got sunburned," and "I'm tired, so I'm going to bed early tonight."
Review the definition of a semicolon: a punctuation mark that's used to separate independent clauses in a sentence. Then give students additional pairs of independent clauses, and ask them to combine the independent clauses with a semicolon. The pairs could include, "the runner drank lots of water after the race" and "she was extremely dehydrated," "the wind howled outside in the dark" and "it sounded like a terrible ghost," and "the calendar says there are just five days left in June" and "then it will be my birthday." Students may be surprised to learn how easy sentence combining can be!
Once students have a grasp of combining independent clauses, ask them to write their own compound sentence. To make the activity simple, ask students to write a compound sentence stating one thing they'll do this weekend and one thing they won't do. Model the activity by giving an example like, "This weekend I'm going to the movies, but I won't buy popcorn at the theater." Give students time to write their sentences, and then invite them to share theirs with the class.