1. There shouldn't be a one-size-fits-all plans and procedures for every school. Criminals try to learn the routines of security personnel and try to predict an emergency response. Even schools with identical building plans need different protocols for this reason.
2. Some parents might believe their kids are safer with an armed guard or police officer around. Some parents think their kids should learn inside a gun-free zone. Both strategies have there merits and drawbacks, and maybe some communities can have both types of schools in the same town so that parents can have a choice. More than 99.99% of the time, it won't matter whether there are armed guards at a school because school shootings are rare.
3. If a school is going to call itself "gun-free", it should be prepared to enforce it. No matter how tough a law is, if it is not enforced then it is just a suggestion. There will likely be metal detectors at the entrances and security cameras in the hallways. If adults don't have a 2nd Amendment right to bear arms, kids don't have a 1st Amendment right to privacy.