It is not about "armed guards."
Communities add "school resource officers" to their school so there is an officer available to the staff for advice.
As well as for the students to talk to if they are being bullied.
The students and staff can talk to the officers if they suspect criminal activities (drugs, assaults, etc).
It is. an option for the schools districts and cities. It is up to them if they want to do it or not.
Of course an officer at the school can help reduce the risk of an active shooter situation. However nothing is guaranteed.
Not everyone would feel this way, but as a kid, I would have loved to have a cop in my school. I always looked up to them and it would have been nice to talk about things with them.