The exact pre-requisites vary slightly from college to college.
Chiropractic colleges are generally four year institutions.
Some schools permit students to finish in three years if they go to summer sessions. Apart from classroom work, the training includes an internship period usually in the school's clinics where student chiropractors take care of patients under the supervision of chiropractor instructors, and an externship period where students may assist field chiropractors in their offices for a period of time. However, since the externs don't have degrees or licenses yet. The maiority of the school work, however is done in the classroom and the laboratory. A lot of people ask how chiropractic education compares to medical education.