Why?
As with coursework, PA schools will look at standardized test scores. They provide schools with an idea of how well applicants are prepared with the necessary background information. The Graduate Record Examination (GRE), Medical College Admission Test (MCAT), and Physician Assistant College Admission Test (PA-CAT) are the commonly required standardized tests. Typically, schools will accept GRE and/or MCAT scores. The PA-CAT is a very new exam and has not been standardized as an admission requirement by all programs.
My Experience
Scores must be submitted before the application deadline, so I took the GRE the January before my application cycle opened. It was enough time for me to take it, receive my scores, and retake it if I was unhappy with my score. The website listed test locations, dates, and times. I selected one during my winter break. The test was administered on a computer, and I received scores on the verbal and quantitative portions before I left the testing center. The score for the writing portion took a couple of weeks after that.
Advice
If given the choice, I would recommend taking the GRE over the other options. I have friends who spent months preparing for the MCAT and found it incredibly challenging. Until the PA-CAT becomes more commonly used, the GRE is the option that will take the least amount of time to prepare. The required minimum or recommended score on the GRE varies between programs, so check their specifications.