Can I just ask a REALLY stupid question?

In the UK we leave school at 16, having taken as many GCSEs as the school deems we will pass. We can then go on and do A-levels (or whatever they are becoming now) until 18 and then go to uni or get a job. We can do NVQs and GNVQs from the age of 14 (I think, but 14-16 is still in school alongside GCSEs - this is not a bad thing IMO) and learn trades that way. If you are doing a childcare or business GNVQ then you don't do various other topics such as technology or languages (WHY? Child carers NEED to know how to cook and speak IMO) but you do more practical-based learning with no exams, just coursework. Our year 11 is age 15-16 and compulsary education ends there. Years 12 and 13 are still called sixth form, thankfully, and that's a student's choice (or a student's parents' choice as is becoming more frequently the case).

So what happens in Australia? Do you stay on for all the sixth form (age 18 when you leave) or do you stop at 16? And if you have to stay on, when are your exams? Do you do your basic exams at 16 then specialise until 18 or is it a prescribed curriculum until 18 with a mix of subjects?