To find out, researchers take a district full of kids with varying standardized test scores and try to figure out how much of the variance can be predicted by what school the kids are in, what teacher’s class the kids are in, and other demographic factors about the kids.So for example if the test scores of two kids in the same teacher’s class were on average no more similar than the test scores of two kids in two different teachers’ classes, then teachers can’t matter very much.
Rank how many percentile points on average a teacher’s students go up or down during the year, and you should be able to identify the best teachers for real this time.
Add like fifty layers of incomprehensible statistics and this is the basic idea behind VAM (value-added modeling), the latest Exciting Educational Trend and the lynchpin of President Obama’s educational reforms.
The American Statistical Association summarizes the research as “teachers account for about 1% to 14% of the variability in test scores”, which seems about right.
So put more simply – on average, individual students’ level of grit is what makes the difference.
But they all agree pretty well that individual factors are most important, followed by school and teacher factors of roughly equal size.
Teacher factors explain somewhere between 5% and 20% of the variance.
Even though these “school level effects” are supposed to be things like “the school is well-funded” or “the school has a great principal”, I worry that they’re capturing student effects by accident.
That is, if you go to a school where everyone else is a rich white kid, chances are that means you’re a rich white kid yourself.
In order to say more than this we have to have a more precise way of identifying exactly which teachers are good, which is going to be more complicated. Suppose you want to figure out which teachers in a certain district are the best.
You know that the only thing truly important in life is standardized test scores , so you calculate the average test score for each teacher’s class, then crown whoever has the highest average as Teacher Of The Year. But you’ll probably just give the award to whoever teaches the gifted class.
Teacher certification, years of experience, certification, degrees, et cetera have no effect.