I worked at a public school of about 1200 students some years back. An armed, uniformed police officer patrolled the school. The same guy every day. Never any shootings. One thing I didn't like: One day, while my algebra students were taking a test, the officer, the vice-principal, and a woman with a dog came into my room unannounced and said the dog was going to sniff the room for drugs. I objected, saying that they were taking a test. I also told them that it was already obvious to me that none of the students in that class showed any of the behavioral signs of drug use. They did not even acknowledge what I said, and proceeded. As I already knew would happen, no drugs were found. It was a random search. No probable cause.