"This is the quarterback problem. There are certain jobs where almost nothing you can learn about candidates before they start predicts how they’ll do once they’re hired."In other words, the only reliable way to figure out how a quarterback will play in the NFL is to put him in the NFL and see how he plays.
And, Gladwell argues, teaching suffers from the same dilemma. Training, certification, and other requirements typically mandated of teachers turn out to be essentially useless in predicting a teacher's success.
Again, it's the same basic problem: the set of challenges presented by a classroom are so unique and the set of skills needed to successfully manage them is so specific that no test—other than putting someone in a classroom and seeing what happens—can accurately identify who will be a successful teacher. (I've certainly witnessed first-hand exactly how teaching can go wrong and how, despite my good intentions and promising list of skills, I got brutally sacked—metaphorically, that is—by a bunch of twelve-year-olds.)*
* The implication, Gladwell continues, is that teaching should shift to an apprenticeship system in which anyone with a college degree can start teaching and is subsequently judged based on actual performance in the classroom, not on external, largely arbitrary criteria.