Massachusetts case and out in Seattle, where school districts on their own set up voluntary measures to assign students to schools, and in two cases, two courts of appeals have held that this is constitutional on the same theory as the big University of Michigan cases in 2003 that diversity is a compelling state interest in our society today.

NPR: De Facto School Segregation Growing, Study Says

Of the well-known U.S. cases, which represent a diversity of backgrounds, it's next to impossible to say.

CNN: STORY HIGHLIGHTS