As for Switzerland- a/ the information you have is no longer applicable and b/ the army is not for anyone under the age of 18 - NO children at all- so why compare with Army Cadets starting drill and army arms manipulation and use from age 12?
As for compulsory army training- again you are a bit behind the times. Young adults do have to serve, but they can opt for social/environment service, instead of army. Guns are now kept at shooting clubs, under lock and key, or at the army bases. Same for hunting guns.
Under 18s should not be recruited to fight and use arms- here, there, or anywhere. Train them to be disciplined, do sport, all sorts of useful skills (and why not sport shooting at ranges) but NO ARMS training. It is wrong and sheer endoctrination - be it in modern Germany or Austria, Congo or here (for me UK and Switzerland).