The National Guard operates the Challenge programs in many different states. These programs are for teens over 16, who have dropped out of school. The program structure is the same in all states, and it focuses on GED preparation and work skills. The program includes a 5 months residential phase, followed by a 12 months "mentorship".
The residential phase begins with a two-weeks orientation, during which communication between the students and his/her family is allowed only through letters (communication is not restricted in any other parts of the program). The residential phase includes community service, classes in various subjects, such as civics and government, social awareness, etc., GED classes, and vocational classes in subjects such as woodworking, electricity, etc. At the end of the residential phase, students take the GED. Many of them also earn vocational certificates.
Each student is also paired with a mentor. The mentor must be an adult who is not a family member, but who resides in the student's community and can keep in regular contact with the student. During the 12 months after the program, students are supposed to find employment or go to school (that is the program's definition of "success"-- a student who is engaged in meaningful employment or who is in school).
These programs are controlled and operated by the National Guard, but there is no commitment to military service (if students do choose to join the military, however, they will be taken as Tier I recruits (HS grads) and not Tier II (GED receipients), which allows them a greater range of positions to choose from). These programs are also entirely voluntary. They do not accept court ordered students, and during the application process, each student must sign documents stating that he/she is entering the program by choice.
What I know about the Challenge programs leads me to believe that they are beneficial, and that they are not concentration camps in disguise like many other programs.
More information can be found here:
http://www.ngycp.org/