Guns in Schools: Always a Bad Thing?

Common sense says that guns and schools go together like a match and gasoline: they know nothing good can come from the combination.  Joan Peterson thinks, and has said many times on her blog, that the idea of ordinary armed people stopping a school shooting incident is fantasy:

Who are these people that we would entrust to "protect" our children? How will they be vetted? At least we know that police officers are trained for this stuff and are vetted and hired to do the job of protecting us. That is their primary job when they are on duty. It is not a part-time, as needed, and when they are available.

But it is not fantasy.  It has happened in the past, and it could happen in the future.  How many times have teachers or students, legally armed, intervened in school shootings with beneficial effects? At least four times in the 20th century:

• University of Texas, 1966, armed students and faculty.
• Appalachian School of Law, 2002, armed students.
• Pearl, MI, 1997, armed faculty.
• Parker Middle School, 1997, armed citizen.

Utah allows carry permit holders to carry their concealed weapons on K-12 school property, but when was the last time an active shooter incident happened at a Utah school?  There are many more reports of unarmed teachers, staff, and students stopping active shooters.  To me it only makes common sense to allow teachers with carry permits to carry their concealed weapons while on duty.  We trust these people with our children already, so why not give them the ability to repel an attack?