The NCLEX is a licensure exam to demonstrate proficiency. If you don't go through and graduate from a PN program you're most likely not going to be able to pass it. Besides, it is a law that you be a graduate of an accredited RN or PN program to be able to sit for the NCLEX. Besides, I certainly would never want a nurse near me who has never had the appropriate training.
Nursing is not the only profession that requires proficiency exams to be licensed. Physicians, pharmacists and teachers, among other professions, do as well. My daughter is a school teacher and she had to take and pass 2 different PRAXIS exams so she could be licensed to teach math and science.
After you graduate and get your Authorization to Test from your state you can schedule your test. If you fail it, you can take it again. I think that different state BON's have different rules regarding how much time must be between your tests and how many times you can take it without taking a refresher. You'll need to check your state BON website for that info.
Even with passing and graduating from your program you'll need to study and review a lot for the NCLEX. It's not meant to be an easy test. In fact, nursing school
isn't all that easy.....as it shouldn't be...