I agree. The NBME has not released this kind of information to schools for the last 2 or 3 years, ever since the USMLE became computerized. So anyone who tells you where their school's rank is for the USMLE are either 1. making it up or 2. using stats that are at least 3 years old.
I think schools are allowed to calculate their own averages, but the NBME discourages them from doing so or from putting too much weight in small differences, and it's nothing that's typically widely available to the public. I think the change is partially because now students can take the exam at any old time of the year. It used to be administered only twice a year, so it was easy to take a cross section of students who all took the same administration to compare them.
What you may be able to find out is the USMLE pass rates of schools, but I think you would have to ask the school itself for that information.