The main answer you're getting is that the ATC is a really worthwhile organisation to be a part of, be it in uniform or as a civilian. I joined as a cadet in 1965, and have been part of it for most of the following whatever number of years.
The units are all slightly different as they reflect to leadership they have. Most areas may have a couple within easy travel of where you live. If you get a less-than-enthusiastic welcome at one, shop around.
The best part of it (and any youth organisation) will be the kids you get to work with. Taking them flying for the first time is an enlightening experience. Your moire or less push a pussycat into the aircraft, then watch a tiger leap out when they come back! Several of the former cadets I helped train went on to have great careers in the Air Force or civil aviation, some didn't, some came back as instructors! Whatever, to know that you might have had a small part in helping them see their latent potential is a wonderful experience.
I'm getting close to 40 years as an instructor. Whilst there were trials and tears, the majority was great. Try it and see how you get on.
Good luck!