We'd like to incorporate an IQ Test (really more of a common sense test) for our new hires as well as our current employees. Not to weed out those who can't pass, but to pin point who has skills needed to preform a certain task so that we can move them into the positions they'd do well at. However, I feel like for our current employees we might be passing into a grey area with how HR might view this sort of test and discrimination. The test is based on word problems, word definitions, and basic algebraic questions as our business is financially based. Many are questions you'd likely find in a standard SAT test for high school students. We just want to be ethical in issuing a test like this.

I didn't read all of this but it appears to relate to your question.
Are there any contracts or union agreements involved?
http://www.onetcenter.org/dl_files/empTestAsse.pdf