Many electives are offered, and cadets who receive transfer or validation credit may substitute electives, including mentored independent study and research projects for those particular courses. Cadets with a high grade point average (GPA) may also overload during most semesters, allowing them to take other non-prescribed courses. Every cadet, however, must remain at the Academy for four years, no matter how many extra course credits are earned. Every cadet must also take a certain number of classes each semester—usually six academic courses (except for fourth-class cadets who only take five courses their first semester).