There are many cases where SRO were used and didn't do diddley or were just a convenient death by cop resource for the killer as they took out others on their path to glory. It's not the only factor or solution. We need to harden the targets (no or slit windows that are not breachable), better video surveillance, and they need the in-class (or group) bug out shelters. Add SRO, permit those teachers and staff that want to carry and/or have a secure but accessible defensive weapon and suitable training available and they will happen less often. That said, QUIT BLASTING IT ON THE NEWS*. Too many of these are simply copycat and/or looking for martyrdom. If the MSM can kill the LGBTQI+ABCXYZ story, they can kill all the others (pun intended).
There are those that say it's harmful to the children to have so much security, but look at the alternative. I'd also point out that some of us grew up doing drills hiding out under our desks becuase they instilled in us the fear that the Russians were going to nuke us all to crispy critters and we turned out (debatable LOL) just fine. The pussification of America, social media, and the mostly fake MSM all have a large part to play in the current trends.