Wisconsin Center for Education Research, via email:

Until now, no one has tried to estimate the costs of educational adequacy across all 50 states using a common method applied in a consistent manner. UW-Madison education professor Allan Odden and colleagues have realized that goal.
In a recent report, Odden, Lawrence Picus, and Michael Goetz provide state-by-state estimates of the cost of the evidence-based model. The evidence-based model relies primarily on research evidence when making programmatic recommendations. The evidence-based approach starts with a set of recommendations based on a distillation of research and best practices. As implementation unfolds, teams of state policymakers, education leaders, and practitioners review, modify, and tailor those core recommendations to the context of their state’s situation. Odden’s report compares those estimates to each state’s current spending.
Allan Odden and colleagues have developed the first state-level analysis of education finance spending using a model with consistent assumptions across all 50 states plus the District of Columbia.
Odden and colleagues studied districts and schools that have made substantial gains in student performance. They identified the strategies used, then compared those strategies to the recommendations of the evidence-based model. The research found a strong alignment between the strategies and the resources in the evidence-based model and those strategies used by districts and schools that have seen dramatic increase in student learning.
The Evidence-Based Model and Adequacy
When experts discuss education finance, they sometimes use the term “adequacy.” Odden offers this definition: “Providing a level of resources to schools that will enable them to make substantial improvements in student performance over the next 4 to 6 years, as progress toward ensuring that all, or almost all, students meet their state’s performance standards in the longer term.”
“Substantial improvement in student performance” means that, where possible, the proportion of students meeting a proficiency goal will increase substantially in the short- to medium term. Specific targets might vary, depending on the state and a school’s current performance. Yet this goal could be interpreted as raising the percentage of students who meet a state’s student proficiency level from 35% to 70%, or from 70% to something approaching 90% and, in both examples, to increase the percentage of students meeting advanced proficiency standards. There are several approaches to estimating adequacy. They include cost functions, professional judgment, successful schools and districts, and the evidence-based approach.
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Using the national average compensation figures, the weighted per pupil estimated costs for adequacy using the evidence-based model is $9,641, an average increase of $566 per student on a national basis. In 30 of the 50 states, additional revenues are needed to reach the estimated cost level. In the remaining 20 states and Washington, D.C., current funding levels are more than enough.
If all states were to receive funding at the estimated level of the evidence-based model, the total cost would be $27.0 billion, or a 6.2% increase. However, the politically feasible approach would not allow using the “excess funds” from the states currently spending more than that level. Given that, the total cost rises to $47.2 billion (a 10.9% increase) to fully fund the model’s estimates.

Locally, the Madison School District spent $370, 287,471 during the 2009-2010 school year, according to the Citizen’s Budget. for 24,295 students ($15,241/student). I have not seen a Citizen’s Budget for the 2010-2011 period. Madison School District budget information.
More from the WCER article:

Nor does this research address how the funds should be allocated once they are sent to school districts. This is an important point, Odden says, because some states currently spend more than identified in this model, yet do not appear to show the gains in student performance the model suggests are possible.