This page is for initial discussions about mapping training depots / buildings of Military Cadet groups.
"Military Cadets" refers to the various voluntary youth training groups, usually aimed at teenagers ~12-18, that are loosely linked to a branch of their country's Armed Forces e.g The Australian Defence Force Cadets (ADF Cadets) are a personal development program for young people, conducted by the Australian Defence Force in cooperation with the community, which benefits the Nation by developing an individual's capacity to contribute to society, fostering an interest in Defence Force careers, and developing ongoing support for Defence. They are broadly similar to, but also different to, Scouts.
Cadet units will often be located within the grounds of Secondary Schools / Colleges. In some cases, particularly with Private Schools, Cadets actually form a compulsory part of the school curriculum.
In most (all?) countries, Cadets are not actually part of the Armed Forces, have no requirement to eventually join the Armed Forces, and do not receive full military training, although they may have serving military personnel acting as instructors.
"Military Cadets" does not refer to the various forms of Officer Cadets, who are actually already enlisted in the armed forces of their respective country, but are still going through their initial Officer Training courses, before being posted to a unit.
One dilemma is going to be what each of the various Cadet groups are called.
E.G. In Australia, they are known as Army Cadets, Navy Cadets and Air Force Cadets,
while the UK has Sea Cadets, Army Cadet Force, Air Training Corps and the Combined Cadet Force (which combines all three Services) https://www.gov.uk/guidance/the-cadet-forces-and-mods-youth-work
Working on the British-English base of OSM, I suppose that we should use the British names i.e. Sea, Army, and Air Cadets?
How to Map
Personally, I don't think that "Club" is an appropriate term for these groups, and would prefer something like "Association". Interestingly, it turns out that association does actually already exist in OSM and is in use 170 times! https://taginfo.openstreetmap.org/keys/association#values. So, association=military_cadets would also work.
Actual mapping would be as either a node or an area.
213 Squadron, Australian Air Force Cadets
TS Vampire, Australian Navy Cadets
133 Army Cadet Unit
Copying from Alux's earlier ideas, I'd suggest that the normal opening_hours=* tag be replaced by a new tag
e.g. parade_hours=Tu 18:00-21:00
This would help differentiate between the hours the area (e.g. school) is open, and the actual times the Cadets are on parade.
If you know the Wikidata code for that operator, that can also be included as:
Would Cadets, whom I have said are NOT military, also be listed under the military key on the Map Features page? https://wiki.openstreetmap.org/wiki/Map_features#Military
Way to early to talk seriously about rendering (which I know isn't up to me / us!) but would also love some suggestions of an appropriate rendering scheme!
A head and torso saluting perhaps?
https://en.wikipedia.org/wiki/Cadet - be warned that this page doesn't do a very good job at differentiating between Youth Cadets & Military Officer Cadets