One nice thing there is that it seems that they do allow you the opportunity to proficiency out of a lot of courses. Unfortunately, it sounds like you have to wait until the beginning of the term to do it which means taking different courses than most people might take in a sequence until you know if you get the credit or not.
Thank @comfortablycurt for reinforcing my comment about the AP Exams. I was only trying to help him/her by pointing out where he/she can find the information and see that in Engineering a 5 goes a lot further than a 4. Personally, if I could choose the best AP classes/tests for my son to take and get out of, it would be the GenEd ones because you only need 18 of those credits and the classes aren’t in the major. Of course, in his case, they’re not GenEds so he will have to take those courses at UIUC which he of course can’t stand.