Generally, the king and queen are students completing their final years of study at their school (also called "seniors"), while the prince and princess are underclassmen, often with a prince/princess for each grade. Recently, some high schools have chosen to add categories, such as duke and duchess, to extend the representation of students to include a category in which students with special needs are elected. In high school, 17- or 18-year-old students in their final year are represented by a king or queen; in college, students who are completing their final year of study, usually between 21 and 23 years old.