During legalized racial segregation, students were assigned to schools based on race. Whites and blacks were educated in separate facilities. In 1954, the U.S. Supreme Court ruled that this practice was no longer tolerable in the landmark case Brown v. Board of Education.

Fifty-two years later, some students still are being assigned to schools based on race. Monday, the Supreme Court began hearing oral arguments for lawsuits filed by white parents in Seattle and Jefferson County, Ky., challenging their school districts’ use of race in assigning students in an effort to achieve “racial balance.”