(My apologies for the wall of text I did my best to shorten it but it didn't really work
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While you or your friend are thinking about cadets or the reserves to strengthen your application to the Royal Military College why not also look into some volunteer work in your neighborhood at the same time? I know of one person from my area who was accepted to RMC who was an air cadet but he also played sports and volunteered at places like soup kitchens and held down a part time job all while keeping up his grades.
Now I am not a recruiter or RMC student or even a Military member so I know I am outside my lane with this and possibly mistaken but it would seem that he was probably accepted into the CF for a lot more then just his being a member of cadets.
And I'm not attempting to talk down on cadets I was a cadet I feel it is a fantastic youth program and can provide a great summer job but I feel you should look at the bigger picture rather then focusing purely on whether reserve service or cadets will help you get into RMC
Regardless of whatever community you live in I guarantee you there are lots of options out there for volunteer work If your old enough why not look into volunteer firefighting? most depts that run what is called a junior training program usually recruit at I think sixteen. You can gain medical and rescue experience and practice teamwork. Another benefit of firefighting experience is with all the ball busting and jokes that happen around the station I promise you will develop a very thick skin.
Quite a few communities run ground search and rescue teams I am not aware of any real age limit to join but I might be mistaken as it could depend on your province. In GSAR you can again gain medical experience you can learn map and compass and learn to work in a team you will also gain leadership experience if for example you are called on to lead search parties and most importantly you get to help people.
And you don't even need to do the super sexy rescue work and wear the cool jumpsuits to help people go to your local food bank or legion see if they have any small jobs you could do to help out you obviously wont be able to do any bar work due to age but I'm sure you can find someway to help out
All of this is stuff that can go on a resume or in your case a school application plus it builds character and lets you give back to the community. And you can still join the reserves or be a cadet while doing this you just need to learn to balance a schedule. And most importantly remember if your in grade 12 hoping to go to a university of some sort don't forget to focus on your school work I learned that lesson the hard way so please don't make the same mistakes as me.
My apologies for the wall of text hopefully my message is clear though I'm sure it isn't
Cheers
SS
P.S. To the staff if you feel I am either mistaken or I have stepped too far outside of my lane please accept my apologies