There is a solution to these shooting but it is complicated, multi-faceted, and will take a long time to bring to fruition. The best start is to do away with these school "no gun" zones. Then arm and train teachers, staff, and admin to carry and to confront a shooter. I did not, repeat, not say force people to carry a gun but those that want to ought to be able to.
If that hero coach had been armed he might have been able to stop the shooter. Then, maybe not, we will never know. Remember that those in the school called 911 to bring those with guns to the school, but way too late.