Is there any good evidence that the main problem with our schools is bad teaching? In other words, if you're going to spend money on improving educational outcomes, should you spend it on "better" teachers or on something like early childhood interventions, as per arguments like this:

http://motherjones.com/kevin-drum/2011/03/james-heckman-educ...

(Ignoring for the moment that spending people's tax dollars on better teachers is politically more acceptable than spending it on targeted interventions.)