Defense in depth. Same as cybersecurity. No single layer can provide total and complete protection; but rather each one, while individually defeatable, slows down the attacker enough to give time to recognize they are there and implement a response.It's not new, I could list more but I'm not going to. Schools can be hardened to whatever degree the school board wants. But there is one factor that needs to be addressed. Children are expected to be safe at school. So that means schools are supposed to have some degree of protection for the children. Now we could argue on how much. But at a min my opinion is it should be very hard to gain access/ entry into the school. A fence provides some protection. Locked doors that CANNOT be easily breach provides some protection. Locked interior doors provides some protection. Not being able to see into the WHOLE classroom provides some protection. ALL these things slow down the attacker, maybe even stops them from gaining entry. This gives the police time to get to the schools. If these things cannot or will not be provided them the school board and admin needs to answer why. I think there needs to be a movement on why these shooters gained access into the schools. If the shooter can't gain access to the students or staff then the firearm becomes a non issue. And then the students and staff are safer.