As a side note, it is not like the kids live in the classroom, they are exposed nonetheless - when outside the classroom - to "normal" air, let's say that in a

As a side note, it is not like the kids live in the classroom, they are exposed nonetheless - when outside the classroom - to "normal" air, let's say that in a week they are 30 hours or less in class and the remaining 138 hours they are not. So these magical filtering allows for intellectual improvements when impacting roughly 30/168=17.8% less than 20% of inhaled air?