Williams spoke at a conference called "The Resegregation of Southern Schools?" sponsored primarily by the UNC Center for Civil Rights and the Civil Rights Project at Harvard University.
The conference, which began with a media day Thursday and ended with a full day of sessions Friday, brought together educators and scholars from around the nation.
Topics covered at the sessions included how segregation affects academic achievement, how court decisions have impacted education and if "private choice," or vouchers, hurts public education.
Williams, who formerly worked at The Washington Post and is an analyst for Fox News Channel in addition to NPR, commended the attendees for taking action against resegregation.
He focused much of his speech on former U.S. Supreme Court Justice Thurgood Marshall, about whom Williams wrote a 2000 biography.
He noted Marshall's achievements in desegregating U.S. schools, including arguing Brown v. Board of Education, a Supreme Court case that deemed legal segregation unconstitutional, before he became a justice.
"If Justice Marshall were here today, he would look at (the attendees) as his heirs," Williams said.
A key to working toward a solution is getting the public to understand both that schools in the South are becoming resegregated and that the trend is detrimental to primary and secondary education, Williams said.
He said educators must be proactive in ensuring that all students receive a quality education.