The Madison School District's four-year graduation rate gap between black and white students closed five percentage points from 2010 to 2011, though the rate for black students remains about 50 percent.
The annual report from the Department of Public Instruction released Thursday also showed Madison's four-year graduation rate dipped slightly last year to 73.7 percent.
According to the data, 50.1 percent of Madison's black students graduated in four years, up from 48.3 percent in 2010. The white student graduation rate declined about 3.1 percentage points, to 84.1 percent.
District officials and education experts said it was unclear what accounted for the changes, and it's difficult to draw any conclusions about Madison's achievement gap from one or two years of data.
"You need to be looking over a period of several years that what you're looking at is real change rather than a little blip from one to the other," said Adam Gamoran, director of the Wisconsin Center for Education Research.
The graduation rates of black and white students in Madison have been a major topic of discussion in the city over the past year.
Supporters of Madison Preparatory Academy, a controversial charter school proposal voted down by the School Board in December, used the black student graduation rates as a rallying cry for the school. The proposal called for a school geared toward low-income, minority students with single-gender classrooms, uniforms and a college preparatory curriculum.
The Urban League of Greater Madison's president, Kaleem Caire, who proposed the school and again vowed Thursday to continue pressing the case for it, said the gap shrank "slightly" but that was more because fewer white students graduated on time and "is not anything that we should be proud of."
"To achieve real progress and faster, we need new approaches embedded within a significant systemic change initiative that employs multiple strategies," Caire said in an email. "One type of school doesn't serve all kids equally well."
Superintendent Dan Nerad agreed varying strategies are needed, citing his recently updated plan to help close the achievement gap. The plan calls for $5.8 million in additional spending next year and $55.6 million over the next five years on a variety of strategies to raise student achievement.
"I certainly understand that it's not going to be one thing alone" that closes the gap, Nerad said. "We need to be in total more responsive to the complex needs of our kids."
The black graduation rate might have been slightly higher, but for the first time the data included a multiracial category, which mostly includes students who would have been classified as black, said Andrew Statz, Madison's chief information officer. The graduation rate for the small number of multiracial students was 76.8 percent.
The four-year graduation rate, which tracks individual students from 9th grade through graduation, was introduced last year. In past years, and for the last time for the 2010-11 school year, graduation rates were based on the number of graduates, dropouts and those who took longer than four years to earn a diploma. Using that method, Madison's total graduation rate increased to 83.9 percent, and the black student graduation rate increased to 63.2 percent.
For 2012, the state will also report on six-year graduation rates in each district.