I believe in order to be exempted from a class, such as the Chemistry class my son was able to exempt out of, you must get the syllabus from the professor. That one proved a wee bit difficult as the professor was no longer at the university, but DS was able to track down a copy somehow and was successful. So, be sure to have your son keep them just in case.
I also believe that there are only a few classes for which you may gain exemption--and others, like
@kpmom2013 mentions, require placement tests, and you are put in different sections based on the results. For my son, it just lightened the load a wee bit for one trimester.
P.S. Proud Syracuse Orangeman graduate here