Can anyone think of any reasons why a student should not take AP Physics C before AP Chemistry if they haven't had a full high school level course in either?

It is my recollection/experience that you don't need to know chemistry to learn physics at either the high school or college level. My suspicions are that Chemistry usually precede physics because it is not as intellectually challenging for most people plus obviously you need a lot less math (only up to Algebra 2 vs. Calculus) at the AP level.