Jill Barshay, via a kind reader email:

Since President Johnson’s War on Poverty Program in 1965, policy makers have been trying to equalize education spending across the United States. The lofty goal is for schools with lots of poor students to have access to the same resources that schools with rich kids have. But researchers and advocates for the poor have pointed to loopholes in Title I funding that effectively allow affluent schools to operate at higher levels of funding than low-income schools. For example, Marguerite Roza at the Center on Reinventing Public Education found that less money is spent on salaries in high-poverty schools than on low-poverty schools within the same district.
Because there can be so much variation in poverty within a school district (just think about the socio-economic differences between Tribeca and the Bronx), the Department of Education is making a big push to calculate exactly how much each school spends on a student. That might sound simple enough. But like any data project, the devil is in the details.
The issue is, how do you allocate administrative and other centralized expenses among schools? For example, say you have an itinerant teacher who spends a few hours at one school, then moves to another, and then another — each day of the week. To properly figure out how much of that teacher’s salary to attribute to each school, districts would need to create some sort of time-and-attendance punchcard system. But who wants to create such an expensive system or put teachers on punch cards?
I attended a boisterous and sometimes acrimonious session on this topic between district bean counters and the U.S. Department of Education at the NCES STATS-DC 2013 Data Conference on July 18, 2013. Many administrators protested the whole idea of counting pennies per school, saying it was too burdensome and impossible. They worried they would have to waste hours figuring out how to allocate all kinds of centralized activities, from computer servers to buses.

Locally, Madison spends a bit more than $15,000 per student, or nearly double the US average.