Because every other country on the planet when faced with the same kind of issue tightened its gun controls in response - Britain had a famous school shooting which immediately led to outlawing all hangun possession by private individuals, there hasn't been a shooting since(despite gun ownership in the UK being actually relatively high, it's pretty common for farmers to have shotguns). In contrast, whenever a school shooting happens in the US(and it's almost 100% every single day of the year now), legislators propose loosening gun restrictions to solve the issue. With some prominent voices saying that well if only teachers were armed, this wouldn't be a problem. And thus, the school shootings in the US not only happen every day, they are such a normal occurance that no one protests at the idea of automated AI cameras scanning students for weapons or schools having metal detectors or armed officers on site, all of which are insane in pretty much every other society. But no, in US you can't solve that - and I have no doubts that we'll have replies to this very comment explaining why US is so special that these same measures couldn't possibly work or worse - how those daily school shootings are a necessary price to pay for freedom of gun ownership and upholding the constitution.