You are all being far too cynical.
The MOD wanted to pull out of funding the CCF in schools only a couple of years ago (we received the letter) but reversed their decision after lobbying by the schools.
Private schools tend to have Officer Training Corps rather than army cadets
The Officer Training Corps title only appears to relate to University Officer Training Corps (since 1948?).
DS1's private school has CCF (Combined Cadet Force) which appears to be exactly what is offered to state schools, although small divisions may only be able to offer the Army Section. Many divisions offer Army + RAF Sections (especially if several schools join together) and rather less offer Navy Sections as well. DS1 wasn't interested at all but some of his friends enjoy it. Camp weeks (kayaking, climbing, mountain biking, overnight exercises) and Field Days look great fun and Flying/Gliding days look fantastic - marching and boot polishing much less so.
There is still an active idea that if you a bit of a bad sort, the military is the place for you.
Quite a few state grammar schools offer CCF - including my old super selective girls' grammar school.
Lots of schools already have D of E.
DS1's school offer that as well. I would say that you have to be quite self motivated (or have very involved parents) to undertake D of E - often having to seek out your own activities and charity work for example and gathering signed paperwork as evidence. D of E can be quite expensive to undertake - CCF seems cheap by comparison - £45 for a week's camp - all food and activities included, £10 for a gliding day - may well be fully funded for disadvantaged kids.
Some CCF cadets will decide to join the Forces - it is a legitimate career.
www.bromptonacademy.org.uk/220/ccf-events
www.thomasdeaconacademy.co.uk/page/?pid=230
www.brookewestontrust.org/news/?pid=9&nid=3&storyid=367
www.priorylsst.co.uk/blog/?pid=156&nid=7&storyid=301