Armed staff tends to eliminate it

You need to speak to the principal. He or she needs to drill the children and the teachers on where to hide or lock down, and where and how to exit the building. There are professionals who will train companies in how and where to hide if there is an active shooter, and your principal should hire them.

That sounds really scary. It's sad that schools need to think about this kind of thing. :( If that happened to me in school, I don't know what I'd do.

1. Ensure students to recognise, if it's a shooting going on. Many may not identify if they heard it first time.
2. What is safe place for them to hide, where they currently are?
3. How to move? Run, hide, etc.
4. How and should try to exist?
5. Many other questions.

As @4meAndyou said, you can consult security professional to give demonstration for staff and students.

I think it's best to hide if you can do so nearby. Otherwise, lay low. If the shooter wants to hit you, running in zigzags isn't going to stop him and you're dead regardless of what you do. Your only hope is that he's not after you, and getting out of the way of his bullets is your best chance.

The children should stay low, but the smart children will run 🤣.I mean, if there's an active shooter, why would you stay there in one place and let him shoot you? You would take your chances running.