You're the one that brought the guard / cop assaulting the kid into it. I see zero value in doing drills, really that’s like us doing home invasion drills here, but refusing to secure our homes and doing anything practical to reduce the risk.
Putting measures into place to actively stop these attacks is infinitely better than drills or passive actions that have no effect. These places are all already "gun free" zones so by that measure alone these things should not happen, but making a law has zero effect on those willing to break said laws. Just like laws to stop someone owning a gun, is not going to stop someone who doesn't give a toss about the laws. By all accounts there are already something like over 300 million legal guns in the US, never mind illegal ones, that horse has bolted, the gov will never get all of them even if they completely revoked the 2A tomorrow and declared any and all firearms illegal.
Armed guards are an effective deterrent even if not 100% successful. If they were not, then there would be no point in securing banks, jewellery stores, politian’s and celebrities with them. I find I rather ironic how people want to pass so many laws (in all sorts of areas) to “protect the children” but when it comes to this, they don’t even warrant the same level as someone who does make believe in front of a camera. Go figure.
I reckon the cost, in lives, psychologically and even monetarily is far worse after a shooting. Honestly if I was a parent of a kid involved in a shooting, I'd go after the school and state for not making the school as safe as possible long before ever considering going after a gun manufacturer. The reality is for whatever cause, these things are happening regularly, it’s the schools duty to make it difficult as possible for them to, yet not become a prison and traumatise the kids in the process. I’m under no delusion that it’s an easy task for them.