The answer is important. Better educational methods can be duplicated in other schools. But no one knows how to increase the supply of motivated families.
In any case, New York is not exactly the norm. A study last year by Stanford's Center for Research on Education Outcomes (CREDO) found that overall, "charter students are not faring as well" as other public school pupils.
These findings may be heartening to liberals who thought the whole school choice movement was a snare and a delusion. But the real world has also demolished liberal notions of how to improve educational outcomes.
More money for schools? Between 1960 and 2005, per-pupil spending in the United States quadrupled, adjusting for inflation. Yet student performance on reading and math tests stayed put.
Smaller classes? As Eric Hanushek and Alfred Lindseth note in their book, "Schoolhouses, Courthouses, and Statehouses," almost three-quarters of the studies conclude that class size doesn't affect student achievement.
Anyone who still puts stock in expanded resources has to contend with the dismal experience of the Kansas City public schools, which got a huge infusion of money when a federal judge essentially took them over in 1986.
Facilities were radically upgraded, classes shrank, new programs proliferated, teachers got raises, and every school became a magnet school. But students didn't learn any more than before. The schools got everything a supporter of old-fashioned public education could have asked for, and they couldn't educate kids any better.
What should we learn from these experiences? Not that nothing works, but that few if any remedies work consistently in different places with different populations. We shouldn't expect that broad, one-size-fits-all changes imposed by the federal government -- such as those offered by the Obama administration -- will pay off in student performance.
From the local school district to the federal Department of Education, humility, caution and open-mindedness are in order. Because right now, the main thing we know about improving schools is that we don't know very much.