There are different writing formats for different exams like the HSPAs, AP exams, and the SAT writing section. The format of writing on the HSPA is the typical five paragraph essay that students are taught since fourth or fifth grade. The writing format on AP exams is more lenient but tends to be around 4 paragraphs with a short, effective introduction. I honestly have not gotten a grasp on the formula of the SAT writing.
Students are expected to master these writing formats if they wish to be a successful writer. Exceptional writers master all three styles; however, most students only have a grasp on one or two writing styles.