Federal law actually forbids the possession of any firearm on any school property, private or public, even by a police officer responding to a school shooting. That absolutely prohibits armed teachers or security guards. School officials also cannot cause any physical harm to any student, even if armed, dangerous, and on a rampage.
School rules prohibiting wireless communication devices, however, do not apply to security guards, administrators, educrats, and certain authorized teachers with specialized security training. Anyone else found in possession of any such device automatically is considered a drug dealer and punished as such. Or so it was when I was in school. With cellular-telephone mania nowadays, things might have changed in the past decade.
Uh, no - this is totally incorrect, in just about every aspect. Law enforcement officers acting in an official capacity are exempt from the Guns in Schools act. So are individuals whose contract with the school or school district permits them to carry guns on school property - this is usually taken to mean private security guards, but it could also mean teachers if the school so desired it. Finally, teachers and school officials do not abandon their right to self-defense merely by entering into the building in the morning - teachers and other school officials have the right to defend themselves against harm from a student, including the use of deadly force if so warranted, just liek any other citizen.