David Brooks writes about a study by Harvard economists Will Dobbie and Roland Fryer on the effectiveness of Harlem Children's Zone schools. Harsh as it may sound, the fact that some charter schools were filled by random lottery assignment makes assessing the effect of the schools much more plausible.
The authors compare educational outcomes among lottery winners to lottery losers, which means they're conditioning on having wanted to enter the school to begin with. They also pursue an instrumental variables strategy on a broader set of kids, with a geographic instrument that's meant to measure outreach or "pitching" of the school, which is an interesting notion.
Can motivation be instilled or does it have to be home-grown within kids? I think they're saying it can be the former.