Columbia University employees won class status in their case challenging the fees and investment funds in the school’s $6 billion retirement plans.

Columbia is the sixth prominent university to face a certified class action over its retirement plan, following the Nov. 8 order by a federal magistrate judge in New York. Judges have certified class actions against New York University, Emory, Duke, Vanderbilt, and Massachusetts Institute of Technology.

Columbia employees say as many as 28,000 individuals are included in the class. Columbia largely agreed to class certification.

At least 20 colleges also are defending lawsuits...