Keeping down cost per child? What are you talking about? The cost per child has skyrocketed in the US over last 20 years, particularly among the worst-performing schools. Baltimore spends more per child than Mountain View. NYC spends more per child than Palo Alto.
There is a certain view, popular among many people, that poor performing schools perform badly because they are underfunded. It has been vigorously spread by politicians, teachers, and activists. Well, we ran the experiment. With enormous federal and state spending, we managed to mostly equalize the spending, and, in many cases, fund the badly performing schools more than the good ones. The results of the experiment are very clear: additional funding, by and large, does not *cause* significantly improved educational outcomes. Any observed correlation between school funding and outcomes is a result of who lives in the area, and who attends the school. The casual arrow does not go from funding to outcomes, but from the school population to both funding, and, in parallel, to outcomes.
Increased funding did improve educational outcomes. It just didn't improve it enough to be considered worthwhile.
The fact is that educational outcomes are caused by a large number of variables. Areas with (historically) poorer schools have less competent (or more corrupt) administrations so money doesn't go as far. Even with good leadership at the top (superintendent or public school committee), if the source of that money is not something you can rely on consistently enough to pay salaries with then you are not going to see significant changes.
Pre-K education is also critical to determining later school performance, as knowing the alphabet and numbers are practically assumed by kindergarten curriculums as they are covered far too far to be more than a review. But we have not tried that yet, so we'll see if that pans out...
Enormous federal and state spending on what, by whom, directed by whom, for whose financial benefit?
The results of the experiment aren't clear at all. Increased spending as was done here hasn't had good results. That's not an argument against spending, it's an argument for understanding why it didn't work, and what could be done about it.
We have data on this too. If, instead of spending at large, you look at spending on any specific thing (school lunches, after school classes, teacher wages, materials, classroom aids, electronic equipment, facilities, etc), you find the exact same thing: nothing we have tried so far has made any significant difference. The proponents of increased school spendings are completely blind to empirics, and their only answer to that is “we just need to spend even more”.