Mary Spicuzza & Clay Barbour:

Wisconsin’s approach to funding schools relies on a confusing and frequently misunderstood formula under which the state picks up the bulk of costs while capping how much districts can collect in state aid and local property taxes combined.
Districts have complained the caps, which are based largely on the number of students a district has, have not kept pace with expenses. In recent years, the state has reduced its share of aid to schools from two-thirds of total costs to slightly less than that, forcing districts to choose between two unpopular options: Cutting programs and services or raising property taxes.

Wisconsin K-12 spending via redistributed taxes has grown substantially over the past 20+ years, as this WISTAX chart illustrates:

More here, via a 2007 look at K-12 tax & spending growth:

MMSD is one of the most expensive public school districts in the state (per pupil spending is highest among the largest school districts). It has been for decades. However, the annual rate of increase in per pupil spending has been very close to the Wisconsin average. While per pupil spending for the average Wisconsin public school district has increased at an annual rate of 5.10%, it has increased by an annual rate of 5.25% in MMSD (see table below). That MMSD costs have risen more should be no surprise, because of cost of living, the loss of students to the growing suburbs (subsidized by state taxes), and the relative portion of special education needs and classroom support needs have risen significantly.

The “great recession” has certainly affected many organizations, including public school districts via slower tax collection growth and flat or reduced property values (which further increases taxes, such as the 2010-2011 Madison School District budget, which will raise them by about 10%).