There are four branches of ROTC and Junior ROTC. Ground pounding Army, deck swabbing Navy, jarhead Marine Corps, and the Mighty Mighty Air Force. ROTC is a coarse of study at certain universities, where the military pays for your education. You are trained to be an officer while pursuing your major. After you graduate you are obligated to five years of service in the officer corps.
JROTC is a high school program that teaches military structure and history. It is taught by retired career officers and enlisted men, generally of a high rank, who wish to be teachers. There is no obligation of any kind for participation. Emphasis is put on integrity, morality (secular), and civic duty. It is completely an elective class, those who participate generally already have an interest in the military. This program prepares a framework for those interested in joining post high school. For those who enlist after JROTC they enter the ranks one rank higher than the general enlistee. I personally decided that after four years in the program that I didn't like the military, but I've never regretted my participation one bit.
As for the instructors participating more with their students. What is wrong with that? I see how it is easy to be cynical about their motivations, but its really not like that. Think of the program as sports team and the teachers as coaches that you really respect.
Hope that answers some of your questions Redcoat