Typically a paralegal school will offer an Associate's Degree Program or a Certificate Program. Also you may find some paralegal schools that offer a Bachelor Degree or a Master Degree.
The Associate's Degree will take around 2 years of study, the Certificate will only need a few months, while the Bachelor's or Master's degrees will require 4 years.
As a whole the job market now require some shape of formal training and diploma. Gone are the days where only some typing skills and a clean pair of shoes assured you a job.
In order to qualify for a Paralegal Certificate you need an Associate or a Bachelor's degree, but some schools require only a high school diploma or a GED.
Also you may want to consider online paralegal schools. The online courses offer many advantages like schedule flexibility and reduced costs. Each course completed is credited towards the degree. A great advantage of online schools is that many will let you pay each course individually...
You may have already discovered that paralegal schools and online paralegal schools are very abundant to say the least. So I recommend that you take a special approach to select your own school and training. If you plan to study in a formal classroom versus an online paralegal school then obviously the physical location of the schools will help narrow the search, because you may prefer an institution that is close to your home. This step being taken I recommend that you analyze the current job market listings and that you note the training requirements for paralegal or legal assistants hiring. This will greatly help you select the amongst the school offerings and will almost guarantee you a strong position on your future job market.
Many job listings will ask for a Bachelor's Degree and/or a Certificate and specialized experience and many Junior Paralegal jobs will require training and some general experience.
Note that most paralegal schools will help you get the required base of experience thru internships or externships with various field experience and hands-on training. Also in the case of a career change, a good portion of your actual experience may apply to one of the many specializations of this field. In most cases only a couple years of related experience will be required.
So if you plan a career change or if you want to qualify for an interesting career you may find that Paralegal Schools are the fast track to a really decent salary (40K to over 100K is the norm) and some neat extras like bonuses and a fair amount of independence on the job.