I looked into that number, and it's wrong. We have a problem, but let's not, whether negligently or purposefully, misstate the number of school shootings.
Look at source. 288 is taken from a CNN article from 2018??? that is stating that number as the total school shootings in the prior decade. The number they should have stated is 77 from their other source. However, even that number is inflated because it includes, for example, a shooting. Behind a school. Of a 27 year old. In his car. On a Sunday. That's considered a "school shooting."
Again, we have a serious problem, but let's also be accurate and truthful about the scope.