Other contributors have said "How long will you be in school for nursing?" is the same question as "What prerequisite must you take for nursing school?" If you believe that these are not asking the same thing and should be answered differently, click here
What prerequisite must you take for nursing school?
Usually nursing schools require courses like Anatomy & Physiology, Microbiology, Statistics, and many other courses. The only way to find out which courses your school requires is to either talk with your adviser or look at the schools website.
You can take the NCLEX as soon as you can get a seat in a testing center. Some schools require you to pass an exam before they will allow you to take the exam but most schools allow you to take it...
It depends on what school and what program you are looking to attend. The basics that are pretty universal are; chemistry, anatomy, physiology, microbiology, nutrition, human development, math, and...