“If Gilraine’s result holds up to further scrutiny, he will have identified what’s probably the single most cost-effective education policy intervention — one that should have particularly large benefits for low-income children. And while it’s too hasty to draw sweeping conclusions on the basis of one study, it would be incredibly cheap to have a few cities experiment with installing air filters in some of their schools to get more data and draw clearer conclusions about exactly how much of a difference this makes.” Vox: Installing air filters in classrooms has surprisingly large educational benefits.