Wis. Stat. § 121.136

(2) (a) In the 2009-10 school year and annually thereafter, the department shall pay additional state aid to a school district if at least 50 percent of the district's enrollment on the 3rd Friday of September in the immediately preceding even-numbered year, as rounded to the nearest whole percentage point, was eligible for a free or reduced-price lunch in the federal school lunch program under 42 USC 1758 (b). (b) Except as provided in par. (c) , the amount paid to each eligible school district in the 2009-10 school year and annually thereafter shall be determined as follows: 1. Divide the amount appropriated under s. 20.255 (2) (bb) by the total number of pupils enrolled in all eligible school districts. 2. Increase the amount determined under subd. 1. by the percentage increase in the total amount appropriated under s. 20.255 (2) (ac) between the previous school year and the current school year, but not less than zero. 3. Increase the amount determined under subd. 2. by the percentage increase in this state's aggregate personal income between the calendar year beginning in the 2nd previous school year and the calendar year beginning in the previous school year, but not less than zero. 4. Multiply the amount determined under subd. 3. by the school district's enrollment on the 3rd Friday of September in the current school year. (c) 1. Beginning in the 2009-10 school year, an eligible school district may not receive under par. (b) less than the amount determined by increasing the amount received under this section in the previous school year by the percentage increases specified in par. (b) 2. and 3. 2. Notwithstanding subd. 1. , if in any fiscal year the amount appropriated under s. 20.255 (2) (bb) is insufficient to fully fund aid payments under this subsection, the department shall prorate payments to eligible school districts.