There was some argument about the style of this graph, but as per Politifact the basic claim is true. Per student spending has increased about 2.5x in the past forty years even after adjusting for inflation.
At the same time, test scores have stayed relatively stagnant. You can see the full numbers here, but in short, high school students’ reading scores went from 285 in 1971 to 287 today – a difference of 0.7%.
There is some heterogenity across races – white students’ test scores increased 1.4% and minority students’ scores by about 20%. But it is hard to credit school spending for the minority students’ improvement, which occurred almost entirely during the period from 1975-1985. School spending has been on exactly the same trajectory before and after that time, and in white and minority areas, suggesting that there was something specific about that decade which improved minority (but not white) scores. Most likely this was the general improvement in minorities’ conditions around that time, giving them better nutrition and a more stable family life. It’s hard to construct a narrative where it was school spending that did it – and even if it did, note that the majority of the increase in school spending happened from 1985 on, and demonstrably helped neither whites nor minorities.
I discuss this phenomenon more here and here, but the summary is: no, it’s not just because of special ed; no, it’s not just a factor of how you measure test scores; no, there’s not a “ceiling effect”. Costs really did more-or-less double without any concomitant increase in measurable quality.
So, imagine you’re a poor person. White, minority, whatever. Which would you prefer? Sending your child to a 2016 school? Or sending your child to a 1975 school, and getting a check for $5,000 every year?
I’m proposing that choice because as far as I can tell that is the stakes here. 2016 schools have whatever tiny test score advantage they have over 1975 schools, and cost $5000/year more, inflation adjusted. That $5000 comes out of the pocket of somebody – either taxpayers, or other people who could be helped by government programs.