But she might want to sit in on a better-than-average math class before stating goals like this: “I wouldn’t keep any school open that wasn’t doing better than average.”
It’s unclear how Clinton is scoring schools for purposes of determining the average, but with such a large sample size (there are almost 100,000 public schools in the U.S.), this likely amounts to a call to shutter somewhere around half of all schools. Were she promising to close schools doing worse than the median, it would be exactly half. But we have to allow for the possibility that a surfeit of poorly performing schools are drawing down the average, which means slightly less than half will be closing.
That’s still a lot of school closings and unemployed teachers and so on. It’s also before you get to the recursion problem—once the first batch of average and below-average schools are closed, the remaining ones will be roughly divided across a new, higher average. The ones at and below it will presumably have to close, too. Eventually we’ll be left with one, very good school, where students will learn the ways this is similar to and different from Zeno’s paradox. But this school, too, will have to be closed, because it will comprise the average on its own, and no school that isn’t doing better than average can stay open.