Expository writing is writing to show knowledge of a subject. The writer needs to write as if their audience knows nothing on the subject matter being written. The more information, details, examples or in other words, the more the writer elaborates, the more beneficial the piece of expository writing is most likely going to be for the reader. In school, expository writing is usually associated with social studies, science and even sometimes math if the school is progressive enough or the standards include writing like in NY. In the adult world, expository writing takes the form of most magazine articles, newspaper articles, as well as reports in the government, financial, education, medical and business worlds. Most likely no matter where adults are employed, if they are considered professionals, they have been required to create or read expository writing.
Expository writing can be done with a formulated process. This means that it is very easy to teach through steps or levels. Once a student learns the steps, they only need to input the information for all other assignments. This way of teaching expository writing works particularly well with SPED students because they need repetition and leveled writing gives them that repetition. Leveled expository writing also allows the teacher to differentiate instruction easily because students in a single class can be on different writing levels but still be writing about the same content.
http://www.teacherspayteachers.com/Product/Leveled-Expository-Writing-System-867302 offers a leveled expository writing system that requires about 5 minutes of teacher planning.