I had the privelege of attending USNA for 2 years before I got the axe. It was a great, great experience. But the academics were brutal: 18 hrs a semester. And there's never enough time to study with all the musters, drill, parades, and sports.
The kids that get accepted to the service academies are all shit hot. And getting in isn't easy. USNA had 17,500 applications for 1250 spots; that's 14:1 for you math types.
http://www.huffingtonpost.com/2010/0..._n_714962.html
As for unruly kids and military prep schools, I'd love to see some statistics. But I'm betting it doesn't work that well. Back in the day, when adulthood came a lot earlier, it may have worked well. But given the extended adolesence of our current society, I doubt it would work.
A better approach in my opinion is the "tough love" "you're on your own" approach. Let 'em fail. Do not rescue them. They'll quickly learn the lesson of consequences. Easy to say, but hard to do.