She responded to an emergency thinking about her students' safety and not "what's the rule". She did the correct thing, and should accept being fired with pride.
Why would she or anyone else want to work for a boss who put the rules before the safety of children, anyway?
In my adventures of teaching, I've never heard of a teacher getting anything but praise if acting on their own kept children safe.
If removing a safety apparatus from schools saves even one life, isn't it worth it?