Dumb parents produce dumb children
A study in South Australia shows that students from low socioeconomic areas have the "lowest education outcomes and poorest achievement". It's been a while since I read The Bell Curve but if I recall correctly its authors postulate that lower socioeconomic status (SES) parents are generally less intelligent than higher SES parents and tend to spawn less intelligent children. If this is true, as common sense would seem to indicate, then these lower SES students' achievement will always be hindered by their limited intelligence. In short, there is no educational strategy that will lift these students to the level of their higher SES peers.
Now I'm definitely no authority on this but it does seem only logical that less intelligent parents beget less intelligent children. And when you factor in the likeliy deficient parenting skills of lower SES parents it seems probable that no amount of effort on the part of educators is going to raise these children to the desired level of performance. Thus it seems that demands for more money to be spent educating the disadvantaged are misguided -- no amount of money and effort can overcome the genetic and environmental factors conspiring against lower SES children.