Well... that is why you have at least 2 independent NGO's overseeing this... it's not like you could ever prevent corruption in any system but if we go that route, there are many ways to make it nearly 99.9% tamper proof.
Though I agree that maybe the extrapolation to foster homes is a bit far reaching.. there could always be some other, less harsh but still as much hurting penalties for failure to pass the parenting exam. Like tax... or you get coupons for children related stuff when you pass.
Man.. don't get me started.. I could list dozens of incentives for this that could make it work even without sanctions.. my point merely is that becaus the media does not make it a topic we will never get there. politicians would only get negative PR if they tried...