To put things into perspective: over the last twenty years, there have been fewer than 200 fatalities in school shootings (including colleges and universities) in the United States. By way of comparison, during that period in the US there have been about 1000 deaths due to lightning strikes, 25 due to (unprovoked) shark attacks, 3000 due to international terrorism, and 200 due to domestic terrorism. So we really ought to be more concerned about lightning and box cutters than about handguns.
You're comparing apple to oranges. You compare the total number of lightning related fatalities to a fraction of gun related fatalities (those that occur at schools) and conclude that lightning is a greater concern than firearms. I think it would be more accurate to compare the total number of lightning fatalities to the total number of gun related fatalities. Either that, or count only the number of lightning related fatalities that occurred at schools.