This is admittedly 27 years old, but at the time Savage Inequalities was written, the range was anywhere from $3k-15k/student: https://en.wikipedia.org/wiki/Savage_Inequalities. I don't remember much of the book, but I remember the description of East St. Louis: raw sewage repeatedly backing up into the schools.
Which is comically high all around. Montgomery County, an expensive DC suburb where housing is more than most of Westchester or Long Island, spends about $16k. Baltimore spends the same, with lower local funding being offset by much higher state and federal funding: https://www.empirecenter.org/wp-content/uploads/2017/05/sbs1.... Fairfax County, VA, routinely the highest or second highest income county in the country, spends $14k.
Cherry-picking a few NJ schools doesn't show much. It would be nice to see an aggregate comparison. This article does that at the state level, and is somewhat conciliatory to your POV. https://www.huffingtonpost.com/2015/03/13/arne-duncan-school.... That said, another commenter pointed out that aggregating by state is doesn't really capture what we're interested in.
I highlighted Camden and Great Neck specifically because they were specifically named in the book cited by OP, and show how the funding gap has closed since 1991.
As to the idea that aggregating by state doesn't capture what we're interested in: the second image in your link shows that, accounting for federal funding, poor school districts get more money in almost every state, including most of the most populous ones: California, Texas, Illinois, New Jersey, etc. The only populous states where poor districts receive less than rich ones are New York and Pennsylvania, and in both states the delta is less than 10%.
Now, if you're talking about comparing between states, that would be very misleading. All it does is set up specious comparisons: e.g., Baltimore, MD gets half as much as Scarsdale, NY, conveniently ignoring the fact that the rich MD suburbs around Baltimore also get half as much as Scarsdale.
It's not misleading. If each state is internally equal, but richer states have much higher funding, that's still a case where richer districts get more funding, just not one that's visible within any one state.
Something related has happened in recent elections: higher income is correlated with voting Republican in every state, but richer states are typically bluer. So if you aggregate by state, it looks like there's no relationship, but if you aggregate by people, there is one.
Returning to school funding, the complicating factor is that so far as costs of construction and labor are higher, New Jersey arguably would spend more per student than Mississippi in a completely equitable world. Because of that, I said that the map was somewhat conducive to your point of view, but there's still a lot of work to determine the net effect.
> If each state is internally equal, but richer states have much higher funding, that's still a case where richer districts get more funding, just not one that's visible within any one state.
The U.S. isn't like the EU, where there are "rich" states and "poor" ones. Adjusted for purchasing power, the states are fairly closely clustered in terms of income: http://1.bp.blogspot.com/-vwpy8_glsgc/Vi5llZ9ZILI/AAAAAAAAIv.... New Jersey and Mississippi differ by about 25%, whereas Camden and its rich neighbors differ by 600-700%.
That means that if school funding within states is even, there is a pretty low upper bound on how big the disparity can be between "rich states" and "poor states."
I see what looks like $26k vs. $38%, so that's more like a ratio of 2:3, isn't it? That said, it puts an upper bound on how large the discrepancies could be.
