Electives become available after year 3 for all users. Electives are accessible through /elective
In years 3-5 you have 5 electives only. You are required to take the core classes + at least two of the electives on this list. You will be able to year up only after you complete all exams for core classes and your selected electives.
After taking the O.W.L.s you are only able to select courses in which you received an E or higher on your exams. If you received an A or below on ALL your exams, you will be graduated immediately. If you have not, it will move you to year 6.
In year 6 or 7, if you deselect all electives and meet the requirements of experience and points, you will be graduated immediately. Otherwise you will only need to take all classes and exams for any classes you selected (previously core or otherwise.)