  Hey that's a very good question and interesting topic. Yeah some school may offer a credit system in which a 3 may get you into a basic class, and 4 or 5 a more advanced class. But in order to eliminate 5 or more credits, most schools has to see that you have at least a 4 or 5 on most AP exams. UW is a very typical example of this AP credit system. Here is a link to see how much credits UW offer base on your AP scores: urlLink UW AP Class Credits 
