There's not a straight forward easy way answer how long nursing school is; the shortest amount of time one could do it post high school and while taking classes all year round would probably be about 2-3 yrs. That would be an 18-month program at a Univ. where at least a year's worth of prerequisites were already taken.
In all time combined and if all goes as planned, it will have taken me about 5.5 - 6 yrs to get a simple Associates degree. I have a prior Bachelor's but no science, basically started over. 1.5 yrs prereqs, 2.5yrs waiting list, 2yrs for Associate's degree.
If you're not too bored already with that explanation, see below.
In the US we have many different titles for our nurses; RN, Registered Nurse is the most common type and what most refer to when they say "nurse". RN is actually a license, they are registered by the board of nursing for the state in which they live/practice.
The minimum amount of school to be able to take the exam for RN's is approximately 3-4 yrs post high school, but it can be done with only a "two year" Associates degree. There's about 2 yrs of prerequisites, like Anatomy & Physiology, chemistry, microbiology, etc...
There is a waiting list in most counties in the US to get into the "two year" schools (community colleges); I waited over 2.5 yrs after finishing my prerequisites.
There is a lesser qualified degree, known as an LPN, Licensed Practical Nurse. They are becoming antiquated in hospitals and relegated to nursing homes (Long-term care); they mostly administer medication and oversee assistant nurse staff.
There are many higher level/advance practice nurses: Nurse Practitioner ("NP"), Nurse Anesthetist, Clinical Nurse Specialist's can all prescribe medicine in the US, and do so somewhat autonomously. Those are the highest paid usually averaging well over $100K after establishing themselves.
In all time combined and if all goes as planned, it will have taken me about 5.5 - 6 yrs to get a simple Associates degree. I have a Bachelor's but no science, basically started over. 1.5 yrs prereqs, 2.5yrs waiting list, 2yrs for Associate's degree.
To get around the waiting list, you could do it all at a University and probably find one that has a 3yr Bachelor's program that takes care of every qualification. Last time I priced one of those, Grand Canyon University, I estimated a total cost of $75k in student loans (that was after the automatic scholarship (good grades) they would have given me of $6k/yr.) <-- ouch
My current route will cost me less than one-third of that (I'm including living expenses too).
*for those fluent in Spanish (here), they can bypass the waiting list, because they are in "need".