I'm all for having willing, competent teachers armed. That said, here's what I was told about one of those CO school districts who were going to do it. They had a group come in to do the training. Don't recall where they were from but they held a meeting and invited any staff member who had any interest in participating or just wanted info. The first question the trainer asked was along the lines of "do you think you could shoot a young person who you have known or taught for several years, if necessary?". He told them if they had doubts about whether or not they could do that, they shouldn't be in the program.
Those armed teachers need to be the real deal!