Hamish,
I am asking about how the flight screening program works between the basic and advanced courses and on how people are ranked within them?
You're grouped into one of three levels based on your "residual" flying experience. The documentation explains how this all will work(as well as this thread). Basically the three courses have slightly different syllabi that assume a different starting point. This will all be sorted by PSA from the hours you declare on your sheet, so be honest. As MajesticCasual said, the assessment is not of your flying ability, but rather of your learning ability.
I am keen to give gliding a go but a bit unsure at powered flying (costs) and the benefits that previous flying experience will have on helping me get through the processes.
Everyone in this thread makes different claims here. In my personal opinion, having two hours in the air before heading to Tamworth was very helpful. This also helps to demonstrate some motivation. Gliding experience is counted as half time because it is naturally different to powered flight. I would suggest if you are keen to do it, give gliding a go at the very least.
The previous flight experience will help develop your control skills of an aircraft and build up some instincts on how to "feel" what the aircraft is doing. You'll find the intensive two weeks at FSP will develop these skills markedly.
If it means anything I want to go through adfa after I finish year 12.
ADFA entrants are usually coursed with other ADFA entrants. If you're finishing Year 10 now, you'll want to start your application process at the end of this year so you can go on Flight Screening during a holiday in Year 12. Be mindful that this will be difficult and affect your study, so be prepared.
If you have any questions about the application process, I am all ears. Naturally those who have been on Flight Screening will be tight lipped over the assessment and OSB elements, but everything else is fair game. the guys over at ausmilitary forums have fantastic threads about the application process too. I highly suggest you give them a read.