Law Dean Thomas Geu didn't worry too much in 2014 when the percentage of J.D. graduates at his school who passed the July bar exam on the first try dropped by about 20 percent.

The pass rate at the University of South Dakota, which he'd led since 2011, fluctuated from time to time, so the decrease to 70 percent seemed like a temporary blip that would quickly correct itself.

But Geu realized he had a serious problem on his hands the following year, when that first-time South Dakota pass rate dropped another 20 percentage points, landing in the 50s. He found himself among scores of law deans across the country suddenly grappling with significant drops in bar pass rates, even when he didn't fully understand why they had fallen in the first place. The rate at his school bottomed out on the July 2017 exam, when just 46 percent passed the exam on their first attempt—roughly half the rate from four years earlier.