From Andrew Coulson at Cato@Liberty, by way of Coyote Blog:
I would prefer if both vertical axes on this chart ran from 0, rather $3500 and 250 points. The math NAEP is scored from 0 to 500, I believe the reading is the same. That would be slightly more honest, though it would still show an order of magnitude increase in spending vs a flat trend in achievement. It's also not made explicit from that chart, but the spending figures do appear to be per pupil, not aggregate.
Coyote makes the following observation: "It is interesting that among the left, this chart is proof that we need to spend more money while the exact same chart in health care (say with scores replaced by life expectancy) is proof we need to spend less money. In fact, the health care chart would look better, because at least there the key metric of quality has increased over time."