Photo by Flickr/Joe Shlabotnik

There's evidence that New York's famed magnet schools--Stuyvesant, Bronx Science, etc--do not improve outcomes for the students who attend them.  If you look at the marginal kids who just barely made the cutoff on the entrance exams, and compare them to the marginal kids who just barely missed getting in, there's little difference.

Of course, it's possible that all the gain is at the top--that while the marginal kids don't benefit much, the best kids benefit a lot.  But honestly, it doesn't strike me as all that likely.  Matt Yglesias has the sharpest summary of the results:

Consider it your daily reminder that when it comes to education, good outcomes are not the same as great teaching. The most reliable way to amass impressive alumni is to screen for impressive freshman. But at the policy level it's more important to identify institutions that are unusually good at helping people learn, not institutions that are unusually good at screening.

This doesn't mean that schools don't matter at all. For starters, there are almost certainly threshhold effects--Stuyvesant is about as good as the sort of high school that the kind of kids who can get into Stuyvesant usually attend.  Most of those kids are probably not coming from the South Bronx.

For another, there are schools that seem to make a difference for poor kids (yes, even when you control for selection effects).  Maybe it's all outliers, but places like KIPP really do seem to be doing something right (as best as I can make out, providing a lot of discipline, and extended school hours).

But it seems eminently possible to me that those threshold effects are something like ceilings--the most gifted kids with the most motivated parents simply don't benefit much from being given an enriched environment.  And it seems perfectly clear to me that we should probably give expensive magnet programs a lot more scrutiny than we usually do.