There are certain jobs [like professional quarterback and teacher] where almost nothing you can learn about candidates before they start predicts how they’ll do once they’re hired.Gladwell thinks pushing for "higher standards" is useless because the standards fail to predict teaching ability:
Test scores, graduate degrees, and certifications—as much as they appear related to teaching prowess—turn out to be about as useful in predicting success as having a quarterback throw footballs into a bunch of garbage cans. . . . we shouldn’t be raising standards. We should be lowering them . . . Teaching should be open to anyone with a pulse and a college degree—and teachers should be judged after they have started their jobs, not before.Read the whole thing.
UPDATE: It's interesting to compare this advice with some McKinsey findings from a year ago (The Economist, 10/18/07). McKinsey says there are key three elements of good schools: " get the best teachers;  get the best out of teachers; and  step in [quickly and aggressively] when pupils start to lag behind."
Here's the part about getting the best teachers:
So, it seems there are at least two different ways to recruit consistently good teachers: the Gladwell way or the McKinsey way. At present, I don't think Baltimore County is doing either.
McKinsey argues that the best performing education systems [outside the U.S.] nevertheless manage to attract the best. . . . [Some] do this in a surprising way. You might think that schools should offer as much money as possible, seek to attract a large pool of applicants into teacher training and then pick the best. Not so, says McKinsey. . . . In practice, the top performers pay no more than average salaries.
Nor do they try to encourage a big pool of trainees and select the most successful. Almost the opposite. Singapore screens candidates with a fine mesh before teacher training and accepts only the number for which there are places. Once in, candidates are employed by the education ministry and more or less guaranteed a job. Finland also limits the supply of teacher-training places to demand. In both countries, teaching is a high-status profession (because it is fiercely competitive) and there are generous funds for each trainee teacher (because there are few of them).