D-Ed Reckoning has some of the stats I referred to in this post which discredit the supposed relationship between public school funding and student achievement. In particular, check out this scatterplot for the 501 school districts in Pennsylvania:
An R2 value of 0.01? Ouch. And, as Ken notes, even at the highest levels of funding you don’t have a consistent trend of high student achievement but rather two trends, one going up and one plummeting down. So, one last time: Higher funding for public schools does not correlate with higher student achievement, despite what our intuition (and various advocacy groups) would suggest.