[paulmd]

that may be true for colleges looking at local feeder schools ("northwestern knows that my high school doesn't have grade inflation"), but I don't know how that idea scales nationwide or internationally. To steal an example, how does a college in Seattle know that a high school in Illinois has grade inflation or not? is that tracked anywhere centralized?

you could certainly look at past performance of students from that school but that turns into a "legacy system with more steps"...