A reader sent me this article from the New Yorker:
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 sounds about right. You would learn as little as possible with the bad teachers – maybe half what you should, while the great teachers inspired you to go beyond the curriculum and learn for its own sake.
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.
This is very much in accordance with the NZ research recently referred to.
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.
I’d rather use that money to pay good teachers more.
Hanushek recently did a back-of-the-envelope calculation about what even a rudimentary focus on teacher quality could mean for the United States. If you rank the countries of the world in terms of the academic performance of their schoolchildren, the U.S. is just below average, half a standard deviation below a clump of relatively high-performing countries like Canada and Belgium. According to Hanushek, the U.S. could close that gap simply by replacing the bottom six per cent to ten per cent of public-school teachers with teachers of average quality.
And not everyone can be a great teacher. But indeed we all know from our own experience that there are some people just not suited to be a teacher. So encouraging them out of teaching (by keeping their pay lower than their collegues) and replacing them even with average teachers will have a massive effect,