One reason might be that according to statisticians the LSAT is only very correlated to bar passage rate until you get LSAT score of 150+, which is about the 50

One reason might be that according to statisticians the LSAT is only very correlated to bar passage rate until you get LSAT score of 150+, which is about the 50%th. Essentially, getting smarter stops helping you pass the bar after you get to about average. This makes sense because the bar is a minimum competency test. So a school having the class drop from 170 to 160 shouldn't have much of an effect on the passage rate. But if they start letting in a large number low LSAT scores (below the 150 threshold) you'll really decrease the passage rate. Even if the median is still the same.