I gave my daughter the kindergarten CAT (which is the youngest version of the test I have been aware of) when she was 3.5. That was several years ago. I don't have a copy of the exam, as I had to return it after administering it, but I remember that she knew some things I didn't expect her to know, and there was one area which she'd never been exposed to and she got all wrong. I don't want to give specific examples lest I invalidate the test, but it was eye opening. She did very, very well.
I don't know why you'd need to pay the test center to give the CAT. You can pay less and do it yourself by ordering through Family Learning Organization online. You do need to state that you are a homeschooling parent, but it sounds as if you qualify.
good luck!
