A group of New York City public school students ditched class with a teacher Wednesday to take part in a pro-Palestinian rally — where the youngsters waved deeply antisemitic signs suggesting the world needs to be “clean” of Jews. Several high school girls from Brooklyn’s Urban Assembly Institute of Math and Science for Young Women brandished unsettling signs reading “Please Keep the World Clean” above an illustration showing the blue Star of David in a garbage can. The group of about 20 students, who participated in a pro-Palestine student walkout with their teacher in Manhattan’s Washington Square Park, were also...