Earlier quoted context omitted.
That's a cumulative 0.7% chance over 18 (or 22?) years, or 0.035%-ish per year. Not only is that not the right way to think about things even if shootings were random, the numbers aren't correct. The Edweek numbers are doing what they were designed to do, which is mislead you and parent / grandparent. They are advocacy numbers, deliberately distorted to make things seem as bad as possible in order to drive clicks to…
> School shootings […] are vanishingly rare in the U.S., a nation of 300,000,000 people. Do you have any sources you can cite? What exactly makes you say that the Edweek numbers are inflated or distorted? (I am genuinely curious.)
You can follow the edweek links to look at their data. It gives enough detail on any given incident for you to make your own call about whether it's included for political reasons or actually representative of the type of thing parents might fear.
Mother Jones maintains a database of mass shootings int the U.S. that would include school mass shootings, and they (to their great credit) use non-crazy criteria to determine what to include: https://www.motherjones.com/politics/2012/12/mass-shootings-...