Schools don't have to publish their average results, and most try to keep them fairly secret. If there were an easy source for this information, you could bet US News would add it to the rankings. As it stands now, you can't even find percentile information for USMLE test-takers, much less school averages. Generally when you show up for an interview, the school will give you a number, or people will say, "They don't give us the exact numbers, but we know we do well on the USMLE...". I know that they're different styles of tests, but my bet would be any school with above average MCATs will in general have above average USMLEs.