UK’s Army Cadet Force
Here in the states we have JROTC. In the UK and Canada they have the Cadets which have been around in one form or another since 1859. Made up of some 46,000 cadets and 8,500 adult volunteers in over 1,700 locations, these youth age 12-18 learn everything from basic to advanced small unit tactics, land nav, buddy care, and of course the standard marching and military courtesy expected from such an organization.
However as you see in the below Vice doc, they are pretty squared away for a bunch of kids.
–It should be noted that, during the great invasion scare of 1940, the Cadets were in many areas issued ammunition and helped train the local home guards before Dad’s Army was fully set up.