"Evaluations ... show that the payback of early intervention to society [from investment in vulnerable children] is huge." The crucial word is "vulnerable". In the US there has been a great deal of programme experimentation and research, which has identified those approaches which are most effective. The benefits to families, individuals and society become primarily from addressing families in which the children have a high likelihood of going to gaol, a low likelihood of regular/any employment; the gains come from changing these likelihoods. As Alice says, it is early childhood which is crucial: the costs of later attempts at remediation are much higher, and the chances of success much lower. Inculcating a pattern of learning at an early stage is crucial.

One of the leaders in this field is Nobel-prize-winning economist James Heckman. Kevin Rudd has completely misrepresented Heckman's work as supporting widespread intervention and middle class childcare provision - I know of no evidence which supports such an approach.

Veritas, Country Gal - many, probably most, of the successful US programs are directed at the dysfunctional families which you both (I think) see as most in need, and (from memory) involve in situ work more often than removal of children.

My wife has worked with children excluded from school because of their behaviour, all coming from families in which early intervention would have been indicated, some gains made with these children, but even so most appeared likely to go on to emulate their parents' drug use and criminality - again, the early years are crucial.

My own early life was much better than that of the children under discussion, although it involved time in bomb shelters (1942-44; trivial), a traumatic family break-up (1944) which led to me being suicidal as an adult, missing out on much normal socialisation and living in poverty. Saving factors were my mother’s strong moral code and belief in education, although both would have been wasted when my (unrecognised) fear of rejection etc overwhelmed me. (My life was saved by external intervention, but not of the type discussed here!)