Review simple sentences learned previously. Simple sentences might say something such as "My mom is a nice person." These are the type of sentences students should already know about from second grade. Teachers can start the review by providing identification worksheets on nouns, verbs, adjective and pronouns. Otherwise, teachers can have the students write a paragraph about any preferred topic, such as summer vacations.
Read a paragraph of related simple sentences, which are choppy. For example, read a paragraph that says "My mom is a nice person. My mom sings to me. My mom tells me stories." This reviews the sentence skills students have learned in lower grades, and it allows the students to hear the choppy flow of the sentences. By third grade, students know enough about reading to understand that the flow does not sound the same as a written book or story.
Introduce conjunctions used to combine sentences. Tell the students that a conjunction is a word to combine sentences, verbs or ideas. Give students an example, such as the conjunction "but" or "and." Give the students a list of conjunction words. Some words students will recognize while other words might be new vocabulary. Show students how to determine the most appropriate conjunction to put the sentences together. For example, read two sentences to the students and ask whether they think the word "but" or "and" is more appropriate to put the ideas together.
Show students how to combine the sentences. Write the sentences on the board and cross out the parts of the sentences that are removed in the complex sentence. Write the sentences on the board with the removed spaces and a line showing where a word is missing. Have the students pick words for the blank spaces and read the sentence out loud. If the sentence is correct, tell the students. If not, ask them whether it is correct or how it could improve. For example, the previous sentences might combine to read "My mom is a nice person because she sings to me and tells stories." This combines the three sentences into one single sentence using the conjunctions "because" and "and." Tell students how they might use a comma instead of a word, such as writing "My mom is a nice, strong and pretty person." Explain that the comma replaces the word "and."
Give the students practice worksheets to combine sentences or assign a short essay so the students can practice writing with conjunctions and commas.