Guns In Schools?...churches, malls, movie theaters?

After the 26 murders at Sandy Hook Elementary School, some political leaders have recommended that police should be on duty in every school in the nation. There are approximately 100,000 public schools and nearly 35,000 private schools. Will the policeman or policewoman be in the right place at the right time in a school building?  Should schools have limited access only, with police on duty at those locations? Should metal detectors be installed in all 100,000 public schools? Should teachers or office staff be trained and have carry permits and have a handgun or other weapon in their offices? Mass murder has occurred in movie theaters, churches, malls, post offices, corporate offices and other places.  Should everyone in all those types of facilities be permitted or required to carry a concealed weapon?  What happens when the person carrying has an issue with a co-worker or possibly gets fired?  What stops that person from turning that weapon on his or her co-workers?