The American Bar Association has collected some data about legal malpractice claims and lawyer disciplinary sanctions. The ABA does not apparently try to link the lawyers' failings with their training, however. Tracing those correlations would take a good deal more work.
The ABA also collects data about how well law schools train their graduates to pass Bar exams. Members of the public might have a passing interest in whether the graduates of tax-funded law schools can pass the Bar, granted. But the more direct and intense interest of law students themselves suffices to keep law schools honest on that front. Who, though, cares about whether those same students will, supposing they pass the Bar, serve their clients competently and ethically? Nobody who ranks law schools, it seems.
Perhaps you find that lack of interest troubling. If so, you might consider joining me in contributing to HALT, a tax-exempt organization dedicated to making the U.S. legal system more simple, affordable, and fair. HALT pursues that goal, in part, by trying to prevent the Bar from exercising monopoly power at the public's expense. We should work harder to figure out how well law schools train students to become competent and ethical attorneys. In the meantime, however, we law professors can help to protect the public from our failings by supporting organizations like HALT.
[Crossposted to Agoraphilia.]