Yes. I don't have rigorous data in front in me, but as a society we've become wealthier over, say, the last 60 years. In every community I've every been a part of, talked with others about, or reviewed data on, taxes for schools, as percentages of property values, income, or sales, have gone up. Greater wealth * higher tax percentages = more money/resources spent on schools.
And declining since when?
Though I'm skeptical of using test score data, the US results haven't been pretty from at least the 1970s onward. Anecdotally, however, this seems confirmed by consensus opinion. Education quality and loss of competitiveness of the median high school graduate relative to the rest of the world has been a continuing political issue for decades.
And how much?
There's no way for me or anyone to precisely quantify either part.
As for your skepticism, I simply assumed that readers knowledgeable about modern US history could appreciate the truth of my point based on the weight of their own observations.
