Since the early 1970s, the federal government has tracked the academic achievement of American 17-year-olds.

The results have been essentially flat despite the fact that per-pupil spending has more than doubled, even after adjusting for inflation.

Overall, the correlation between spending and achievement is among the lowest I have ever seen in social-science research: 0.08 on a scale from 0 to 1.

Presented with this dismal national picture, many pundits and elected officials protest that their own states have done better.

The trouble is, there’s been no way to verify their claims. State-level test score averages don’t reach back that far, or, as with the SAT, they aren’t taken by a representative sample of all students.

But there’s a way over this hurdle: State-level academic trends can be estimated all the way back to 1972, and the results aren’t pretty. (See the charts that accompany this post).

The average state has seen a three-percent decline in math and verbal test scores, and a 120-percent increase in real spending per pupil.

The few states that improved their scores substantially tended to be those that were well below average to begin with.

Overall, the correlation between spending and achievement is among the lowest I have ever seen in social-science research: 0.08 on a scale from 0 to 1.

But what's the trick to measuring state academic trends when no ready-made test results exist? Back in 1993, a pair of clever education statisticians developed a method for adjusting SAT scores to account for differences in the test-taking population between states.

By extending and enhancing their technique, I was able to draw meaningful trends for all 50 states reaching back 40 years.

What those trends suggest is that every state in America has suffered an education productivity collapse.

Outcomes are generally stagnant or declining despite massive increases in expenditures. In the best cases, verbal and math skills have improved modestly, but those improvements have been outstripped by much more dramatic increases in real spending.

Perhaps even more telling, state achievement trends have proven to be just as unaffected by the rare multi-year periods of declining spending as they have been by periods of rising spending.

In other words, political and education officials keep making the same mistake over and over: spending more and more tax dollars without stopping to ask if it’s doing any good.

Even if taxpayers could afford to keep that up indefinitely, it would be better for America's children to pause for a moment, and look for alternatives — to see if there are other ways of running and funding schools that make better use of scarce education dollars.

As it happens, scores of studies have looked into this question over the past 25 years. They find that when educators’ fortunes rise and fall according to their schools’ thrift, schools are thriftier.

Entrepreneurial schools chosen by families and funded at least in part directly through tuition are consistently more efficient than bureaucratically run, tax-funded schools.

Can anyone honestly be surprised by this?

At the end of the day, educators are people, too. Unless education entrepreneurs are allowed to profit from finding better and more efficient ways to serve parents and students, taxpayers may as well get used to the status quo depicted in these charts.

Andrew J. Coulson directs the Cato Institute's Center for Educational Freedom and is author of the study "State Education Trends: Academic Performance and Spending over the Past 40 Years."