If you've ever hired anyone, you know that that colleague you get is nearly always quite different than the candidate you interviewed--sometimes better, sometimes worse, but always different.
This interesting paper about teacher quality adds to the substantial but far-from-conclusive literature on what makes for a great teacher. In short, a few previously unstudied teacher characteristics appear to correlate with improved student achievement, but nothing revolutionary.
If you're looking for something on the same subject but with a reduced wonk factor and more talk about college football (seriously), check out this New Yorker article by author of all things curious, Malcolm Gladwell. Other professions face the same recruitment challenge, but they address it differently than those in the teacher-hiring business; instead of big barriers to entry and few back-end check-ins, they open up the floodgates on the front-end and then weed out along the way.