We can start by acknowledging that you are already pushing the line to minimize the issue by trying to make it about physical harm only, not psychological harm of being in an related incident.
Most recent data is from 2022, and indicates there are 49.6 million school aged children in the US. The closest we have to official numbers around children involved in gun violence in school shootings since 1999 starting with Columbine comes from the Washington Post (because, for some reason, the US government doesn't track this). It says that 338,000 children have been involved over this time period.
That comes out to 0.7% of all school aged children have been involved in a school shooting in the US. Your 'bullshit, pulled from your ass, percentage above is 4 magnitudes off of reality. That is the same as you finding a ten dollar bill and loudly yelling "I JUST FOUND $100,000!".
Do better and suck less. This is just around your claims as well, that is setting aside the monstrous view point that any percentage of kids would be acceptable to be involved in school shootings.
You are correct, that was a flaw in my process.
If a child makes it from K to G12, that is 13 years of school. Checking a quick chart showing the number of enrollment in schools from in the 80's and 90's, enrollment was lower. Once it hit 2005, it is between 49m-51m. If we cut the percentage in half to and round down to 0.3%, my statement of the 4x magnitude still stands.
Thank you for considering, checking and bring up that misrepresentation in my previous number.