> There are mounds of evidence that “good schools” in the US—whether traditional private, traditional public, public-subsidized private charter, or public charter—are a product of getting the right student population rather than substantive differences between schools.

I think a lot of this comes down to the metrics used for gauging good schools. Which are usually test scores, graduation rates, and discipline rates.

Assuming that the test scores measure something worthwile, test scores is always reported as a point in time measurement -- but really a progression would be more informative. What I really want to know is will my kid go up or down or stay the same in test scores if they attend school X, it's not super important what the average score is ; especially since the progression may vary significantly based on the input score.

Graduation rates could be low because of many factors outside of school, or could be high because the standards are low, and are often reported only at the high school level but kids who don't graduate high school were often not well prepared at other levels, etc.

Discipline rates can be meaningful, but if one school doesn't expel anybody because all the children are angels, and one school doesn't expel anybody because they haven't noticed the large numbers of murders during recess, the numbers look the same.