I suspect that if this article was accompanied with a simple pair of pie charts representing the class of crimes under which people are imprisoned in the US, and their economic status, it would make a simpler and more honest point. Using poor people to spring people who've committed securities fraud from prison is wrong.
"Spending per prisoner [is] about $50,000 in California, where the cost per pupil is but a seventh of that."
Yeah, if you count the cost of building prisons but not the cost of building schools. And they're really using the ban on trafficking endangered species as an example of a stupid crime? The fact that there are people in prison for using drugs while people who catch/sell/eat bluefin tuna walk the streets freely is an embarrassment to the country. And it's one thing to complain about being charged for the weight of the whole cannabis plant and not just the buds, but complaining about it being illegal to adulterate drugs is beyond me.
Annual per capita costs of incarceration in California: http://www.lao.ca.gov/laoapp/laomenus/sections/crim_justice/...
http://www.lao.ca.gov/analysis_2008/education/ed_anl08006.as...
Education costs are a bit higher than the article suggests, and you are right that they would increase further if building expenses were included. Part of the problem is that most spending is controlled at the county level and many people oppose centralizing education spending or policy at the state or federal level.
Other interesting data can be found at the links provided, albeit a year or two behind the latest budget #s.