Gladwell always sets his premises on the research of others.  Here is a wonderful explanation of why teaching is so critical, particularly given the usual focus on schools and class size:

Eric Hanushek, an economist at Stanford, estimates that the students of a very bad teacher will learn, on average, half a year’s worth of material in one school year. The students in the class of a very good teacher will learn a year and a half’s worth of material. That difference amounts to a year’s worth of learning in a single year. Teacher effects dwarf school effects: your child is actually better off in a “bad” school with an excellent teacher than in an excellent school with a bad teacher. Teacher effects are also much stronger than class-size effects. You’d have to cut the average class almost in half to get the same boost that you’d get if you switched from an average teacher to a teacher in the eighty-fifth percentile. And remember that a good teacher costs as much as an average one, whereas halving class size would require that you build twice as many classrooms and hire twice as many teachers.

What he finds, naturally enough, is that we focus far too much on teacher preparation and far too little on evaluations and interventions — for teachers, not by them — once they are in the classroom.

A group of researchers—Thomas J. Kane, an economist at Harvard’s school of education; Douglas Staiger, an economist at Dartmouth; and Robert Gordon, a policy analyst at the Center for American Progress—have investigated whether it helps to have a teacher who has earned a teaching certification or a master’s degree. Both are expensive, time-consuming credentials that almost every district expects teachers to acquire; neither makes a difference in the classroom. 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.

It should surprise no one that it is hard to predict what makes a good teacher, for there is no single model. Particularly in schools with strong cultures, teachers work within a system — and the same teacher may shine in one system and fail in another (and some systems are so bad no one can succeed).  Gladwell writes “A prediction, in a field where prediction is not possible, is no more than a prejudice” — and prejudice describes our current hiring preferences.

Like many of Gladwell’s pieces, the answer he chooses is not particularly complex.

[Teaching] needs an apprenticeship system that allows candidates to be rigorously evaluated. Kane and Staiger have calculated that, given the enormous differences between the top and the bottom of the profession, you’d probably have to try out four candidates to find one good teacher. That means tenure can’t be routinely awarded, the way it is now. Currently, the salary structure of the teaching profession is highly rigid, and that would also have to change in a world where we want to rate teachers on their actual performance. An apprentice should get apprentice wages. But if we find eighty-fifth-percentile teachers who can teach a year and a half’s material in one year, we’re going to have to pay them a lot—both because we want them to stay and because the only way to get people to try out for what will suddenly be a high-risk profession is to offer those who survive the winnowing a healthy reward.

In my experience, too many school systems already have an entering wage that is apprentice-like, so we need to focus on compensation plans that reward the truly great teachers over the merely average.  Ugly truth number one is that we need to start measuring which teachers are which. Ugly truth number two is that we need to reduce pension benefits and use that money to increase salaries so that we are not underpaying teachers during their working years while rewarding in retirement those that stay for 20 or more years.

Frankly I don’t find the requirement to have four candidates for each teaching job that daunting — we already lose 50% of teachers within five years, we just often lose the wrong ones for the wrong reasons.  Due to the efforts of organizations like TFA, the teaching profession (like all others) is becoming more mobile — one part of a career that may take many turns.  Argue for or against this if you wish, but it is probably here to stay.  But while we see increased mobility for new teachers, ugly truth number three is that we need to give principals more ability to change the teachers they have who are not working.