An emergency situation that turned out to be mostly a false alarm led a lot of schools in Los Angeles to install air filters, and something strange happened: Test scores went up. By a lot. And the gains were sustained in the subsequent year rather than fading away.That’s what NYU’s Michael Gilraine finds in a new working paper titled “Air Filters, Pollution, and Student Achievement” that looks at the surprising consequences of the Aliso Canyon gas leak in 2015.The impact of the air filters is st...