I think you are just trying to find something to complain about. You should be happy that you actually have a job and earn money. If you start work before age 15 it's obvious you're going to get a crappy rate of pay because the awards don't protect you.
It may be hard work wherever you are, but that doesn't mean you should whinge and whine about how little you get paid all the time. Think about the experience you are getting, and if the work is really that bad try not to think about it and just do it. Once you've been at a job long enough everything becomes automatic anyway.
Younger people get paid less because they theoretically have less monatery responsibilities and their time isn't as 'valuable' as older people. Think about it: -
a 14 year old works 4 hours each afternoon at some store, the same as a 17 year old. Now when the 14 year old gets home he maybe has to do a couple of chores and do his easy (and dare I say meaningless) year 8 homework. However when the 17 year old gets home, he has to also do chores and study for his upcoming exams which count towards his HSC.
Therefore the 17 year old really doesn't have time for a job, but he needs the money; whereas the 14 year old may need the money, but he has time for the job.
Also the 17 year old may have expenses unlike the 14 year old. Eg. car, rent (some parents are stingy), school stuff etc.
To say Maccas work is labour is a bit of a stretch, I may have never worked there but I doubt the work is difficult and exhausting - sure it may get hot and you may get tired, but that isn't labour. And slave? Come on.
Be happy with what you have, and if it is above award wages then be really happy! And if you still insist that your work is too damn hard and you're not earning enough money, then quit and find a better job! And if one doesn't exist then why don't you be entrepeneurial and start your own business - or would that be too difficult and slave like?