How many teachers would school reformers have to fire in order to get American schools performing at their best? That's the question researchers Doug Staiger and Jonah Rockoff set out to answer in a study they presented at the Columbia conference.The researchers went through a simulation exercise, building on prior findings about the impact that great teachers have on their students, the fraction of incoming teachers who turn out to be strong performers in the classroom, and the "signal-to-noise" ratio in a teacher's performance during her first couple of years (i.e., how hard it is to tell whether a teacher is bad or just unlucky).
When they ran the numbers, the answer their computer spat out had them reviewing their work looking for programming errors. The optimal rate of firing produced by the simulation simply seemed too high: Maximizing teacher performance required that 80 percent of new teachers be fired after two years' probation.
After checking and rechecking their analyses, Staiger and Rockoff came to understand why a thick stack of pink slips are needed to improve schools. There are enormous costs to having mediocre teachers burdening the school system, and once they get their union cards, we're stuck with them for decades. The benefits of keeping only the superstars is enormous, such that it's better to risk accidentally losing some of the good ones than to have deadwood sticking around forever.
Is an 80 percent dismissal rate practical? One issue is whether there would be enough new recruits to replace all the teachers you'd be firing. Teach for America has been able to fill its ranks with Ivy League graduates year after year, so we know there are lots of college grads who are willing to devote at least a couple of years of their lives to teaching, and 63 percent of TFA alumni remain in the field of education afterward.
Similarly, think how good the LA Lakers would be if they fired all their players besides Kobe Bryant and Pau Gasol and replaced them with guys who are just as good as Kobe and Pau. They'd be epic! Speaking of firing all the deadwood, why do they let idiots like Phil Jackson and Mitch Kupchak run the Lakers when they could just hire some economists who are good with SAS to figure it all out?