No comparative metrics exist for comparing the quality of law department lawyers. What got me thinking was reading about the Law Department of New York City. That Department proudly announced that the percentage of lawyers joining it in September 2005 who graduated from one of the 30 top law schools as ranked by U.S. News & World Report was twice as high as the same percentage from the September 2003 class. Using directories, one could compare law departments on this dimension.
You could also look at the percentage who had clerked, served on a law review, or been an associate at an AMLAW 100 firm. If only we had LSAT scores and undergraduate GPAs.