Hi there
Firstly, keep up the school grades as they will always help with no matter what you try to pursue as a career - for a pilot, usually good maths, science and geography marks are a bonus...
You can try and apply for SAA's cadet pilot program (
http://www.flysaa.com) where you will sit a few psychometric tests etc and if you make it through their system, they will train you up free of charge and offer you a job on completion - however dont get your hopes up yet, yes this is mainly for previously disadvantaged people and they only take on about 10 people out of the hundreds that apply (however you might be the 1 they do accept, so certainly worth trying!). That would be the ultimate for any wannabe pilot but in reality the chances are slim and you may have to do it privately at your own cost! (I believe Comair also have a cadet pilot system? not to sure on that one!)
As for the SAAF, hope you willing to sign a 12 year contract! Besides that yes it is also difficult to get in unless you were previously disadvantaged.
That leaves your option to basically paying your own way. Whoever told you the cost of a PPL was way out, you will be looking to pay about between R35000 and R40000 for a PPL but then remember you wont be able to get a job after that. Your best bet is to do your Commercial Licence (That may cost just over R100000) and then do your instructors licence - hence building up your hours!
You might also consider other options within the aviation industry - ever thought about being an air traffic controller? Try
http://www.atns.co.za and have a look through their website. They will also pay for all your training and it is a fantastic career.
Hope this has helped.