I've been having a mosey through various airlines requirements and the most sensible I've seen was Cathay, tyhey basicall said, Yr 12 (or equivalent) or ATPL's. Which makes sense to me.
The scenario where I imagine it'd be a headache is for someone who has say flown 2,000 hours with virgin and wants to move to Qantas (I know, but it is hypothetical!) and doesn't have year 12. Surely Qantas wouldn't turn them away because of a bloody high school certificate?
Anyway, keep the opinions/rumours/libel coming, it's all good stuff