Seventy years ago this week, the U.S. Supreme Court ruled separating children in schools by race was unconstitutional. On paper, that decision — the fabled Brown v. Board of Education, taught in most every American classroom — still stands. In reality, school integration is all but gone, the victim of a gradual series of court cases that slowly eroded it, leaving little behind. For decades, American schools have been re-segregating. Around 4 out of 10 Black and Hispanic students go to schools where almost every one of their classmates is another student of color.