Well-known colleges and universities in the United States announced this week that they will end the first part of the school year early because of a rise in COVID-19 cases. They will also move final tests out of classrooms and onto computers. Princeton University and Cornell University are part of the group that is closing school early. Students traditionally leave school for about one month after December exams. Both Cornell and Princeton say nearly all of their students are vaccinated against COVID-19. At Syracuse University in central New York, students will need to get a booster shot before coming back to school in January. The schools also said some of the COVID-19 cases are from the Omicron variant first found in southern Africa in November. Kent Syverud is one of the top leaders at Syracuse University. Until recently, he said, the school was feeling good about the part of the school year that starts in January. “But Omicron has changed that,” he said. He added that the school will try to keep students and teachers safe until more is known about the variant.