How weird, was just about to start a thread on this very subject - along the lines of Gizmo's comment: "If you're bright enough to shine at school without having to really work, does that mean you have to learn self discipline later on in life? "
Definitely an issue for both me and dh - neither of us were stretched enough at primary/secondary level, coasted along without ever making any effort ... got to the bit where it really counts, and it all went wrong.
Dh walked out of school before sitting his A levels because he refused to do the homework as he didn't need to do it. He was told, "no, you don't need to as you are very bright, but it sets a bad example to the others so you will have to leave". He re-sat his A levels (well turned up to the exams), got good enough grades to study law, then failed his law degree. He had never learnt (and/or never been taught) how to work - he'd never had to.
I scraped through my A levels and went to Uni to study Behavioural Sciences (same uni as dh!), and scraped a 2:1 (when I could have got a first if I'd applied myself). Tbh I don't think it was so much lack of effort, as lack of ability to work effectively.
We are both soooo keen that the dds don't go down the same route. Fortunately their teacher has got them sussed and is very keen to keep them challenged.