In fourth grade, students learn to use a variety of sentence structures in their narratives, summaries, responses to literature and information reports. They learn to use compound sentences, and may also learn to use complex sentences. Students learn to combine short, related sentences with appositives, participial phrases, adjectives, adverbs, and prepositional phrases. When introducing a new type of sentence structure, the teacher should provide adequate practice in writing sentences before requiring students to use the new sentence type in writing passages. Those assignments should be structured to prompt usage of the new sentence type. In addition, the teacher should provide adequate cumulative review to facilitate understanding and retention as well as exercises requiring the students to revise existing passages by combining sentences and thereby create a new type of sentence structure. Students should be taught not only how to create new sentence types but when to use them. For example, some students will need careful instruction to determine when words, phrases, or clauses should be joined by and, or, or but.
the Reading/Language Arts Framework for California Public Schools)