Several years ago (like 1988 or so) the US gov't published
per capita spending in the public schools by State, along
with graduation rates. Interestingly enough, there was a
significant correlation between per capita spending and
graduation rates. I did the regression analysis myself (my
graduate work is in Mathematical Probability and Statistics
at the University of Texas at Dallas). Unfortunately for the
"spend more, get better results" crowd, the correlation was
negative. OTOH, there is such a thing as "practical significance"
which is different from statistical significance. The correlation
was so slight as to be not practially different from zero,
though statistically significant.