Vista Grande High School in Casa Grande, Arizona, held a lock-down drug sweep on October 31. Students Inmates were confined to their classrooms, then led in small groups to another room where they were forced to line up against a wall and be searched with the help of drug-sniffing dogs. This exercise introduced a new element: Among the four law enforcement agencies involved in the search was a group of prison guards employed by the Corrections Corporation of America, the nation’s largest for-profit prison contractor.