Words can sometimes fail to fully capture the grotesque. But D.C. Council Chairman Phil Mendelson (D) came close when he said it was “shocking and beyond belief” that third-grade students in a D.C. school were directed to reenact scenes from the Holocaust. The incident has appropriately been roundly condemned, and the librarian who allegedly instructed students to act out atrocities — and then not tell anyone — has been placed on administrative leave. It is critical that there be thorough investigation to determine how such a thing could happen. Third-graders at Watkins Elementary School in the Capitol Hill section of...