The Supreme Court on Thursday set new limits on affirmative action programs in cases involving whether public and private colleges and universities can continue to use race as one factor among many in student admissions.

The court held, in a 6-3 opinion written by Chief Justice John Roberts, that Harvard and UNC’s admissions programs violate the equal protection clause of the 14th Amendment.

Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson dissented.

The blockbuster cases put affirmative action, which has been used for decades by colleges and universities to address inequality and diversify their campuses, in the spotlight. The Supreme Court had repeatedly ruled since 1978 schools may consider the race of applicants in pursuing educational benefits from a diverse student body, so long as they did not use a quota system.

Because mediocrity is so much more important than diversity.