You can in Victoria: https://www.vic.gov.au/if-your-child-wants-leave-school-early

Someone who's 30 could conceivably be working at the same position at Coles, as you say, as a 17* year old . (This is the law in Victoria, there may well be 16 year-olds who can leave school in other states).

It's stupid though, because this is MINIMUM WAGE, that they reduce even further just because of your age.

I think it's dumb and they should at the very least remove this minimum wage "discount" (notice how it's in the employers point of view, love the FWC...) for 16-17 year-olds also, as they may be working full time.