Rev. Donald Sensing has a thoughtful post on the subject. He's not ready to have teachers start packing just yet.
I am reluctant to agree that arming teachers is a solution. They didn’t sign up for it when they entered the profession. There is enough on teachers’ plates without expecting them to stay proficient in handgun use. A teacher poorly trained or untrained in effective use of firearms could be just as dangerous to the kids as an intruder. If such a teacher gets downed, then the bad guy has another weapon.
As i see it, having armed teachers in classrooms will increase the number of accidents. If a teacher misplaces their gun (it's been known to happen even to police officers) the firearm will fall into the hands of curious twelve year olds or cocky teen-agers. That is a recipe for disaster.
Keeping schools gun-free is not a good solution, either. In a shooting like Columbine, an immediate armed response will save lives.
Right now, i lean toward permitting firearms in schools where they can be kept secured and away from students. A gun locked up in a principal's office is still better than no guns at all.
Rev Sensing's idea about trained volunteers has a great deal of merit and is another way to address the trade-off between preparation and accidents.
If we go down this road, however, we will need new training to make it effective. The scenarios are a hybrid. You cannot expect teachers or volunteers to become accomplished SWAT operators. At the same time, they confront much different challenges than those faced by a civilian CCW-holder.