I am 22 and I still train at a local club (the same one I have always been at). I train in a group with girls ranging from 10 or 11 years up to my age (the second oldest is 17).
I also still compete, and there are a many older teens and young 20-somethings competing along side me or in lower levels. There is even a woman competing in state level 10 who is 34!! she has 2 kids who come and watch her at competitions!
Don't let age differences bother you..... both you and the younger kids will get used to it. If you want to do gym, then go for it!!
(btw... I'm in Australia too - Melbourne

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