they really shouldn't. firstly why are early school leavers being targeted, not everyone needs to go to university and we should encourage more people going into trades or other pathways instead of people who only go to uni because they get told to (nothing wrong with this decision, but guaranteed if that's a rule, anyone who doesn't want to go to the military will go to uni and no one will want to drop out early and go and do an apprenticeship / take a couple of years to get physical skills and then go into a trade).
secondly, consider the other bunch of early leavers, who may not be in the best place mentally or have issues that might make dropping out of school a good decision. is it a good idea to have these people in the military, not to mention people who aren't even adults yet, or haven't had any real lived experience outside of school? look at other countries with conscription, what ends up happening is many uninterested young people who become alcoholics or worse.
thirdly, conscription doesn't address the underlying difficulties that the adf has (and also why do we even need conscription at this point? there's no war, and if there is one why not just conscript then if ever). what are the actual reasons why they have low numbers, maybe they should increase benefits or do other things to make people interested rather than force everyone into a year of service, when there's probably not even the infrastructure to do so - which ultimately just makes it seem like doing this would just be to funnel more money into the military rather than any other reason