Gibberish. This isn't a systemic problem. It is a failure of one or four trained, paid police officers to do their job. If you include armed security personnel as being part of making the target as hard as possible, then you assume the security personnel will do their job like the DC Capitol police did during the Scalise shooting.
There is no excuse for the four law enforcement officers who were derelict in their duty. Systems don't overcome cowardice.
Do you even know the meaning of the word systematically? It means everything as a whole, it means everything from A to Zm there was no one failure point it failed when The FBI didn’t respond to a nine-one-one call, it failed on several other notable occasions that are being brought out by various sources. Training and doctrine failed or was woefully inadequate, or perhaps did not even exist. That is the meaning of systematically, and it might be gibberish to you, or it probably was also gibberish to those people in charge who took absolutely no proactive approach to protecting children in public schools.
Remember this 9/11, might have been averted if somebody would have listened to a loan field agent who had obtained intelligence that foreign Nationals were training to fly heavy Jets. The FBI knew about it and took no action to investigate it. The result - the Twin Towers came down. This is on a much smaller scale but it’s a tragedy none the less. And