A high school teacher choose to teach the five-paragraph theme because it simplifies writing for the high schools students. High school students are very diverse and depending on the student their writing abilities might not be equivalent to that of his fellow class mate. The five-paragraph theme is not interesting for the reader but teachers use it at a base. Typically you wouldn't give a first grader a multiplication problem you first introduce him to addition as a base for mathematics. After teaching the student addition then you teach the student multiplication. This is what high school teachers are doing for their students they are teaching the writing basics to their students.
