Of the nation's 10 largest cities, eight use armed police in some form. And in the ninth city, New York, officers receive far more training and scrutiny prior to hiring.
Five of those city school districts - San Diego, Los Angeles, Houston, Dallas, and San Antonio - employ their own police officers, who receive comparable training to regular city police.
Chicago, Phoenix, and the San Jose Unified School District base city police officers in some of their buildings. In the case of San Jose, the officers are not in uniform, but rather dress casually in polo shirts and conceal their weapons.
In New York - the nation's largest school system - the city police department's school-safety division staffs the schools with unarmed officers who receive 14 weeks of training, intensive background scrutiny, and drug and character screening. (Armed precinct-based officers, however, also come into the schools.)
The nation's largest cities are by no means alone.
The Council of the Great City Schools, a coalition of large urban districts, surveyed members in 2004 and found that 29 of 37 respondents indicated its officers were armed. Las Vegas, Miami, and Indianapolis are among other bigger districts with their own police forces.