With fans twirling and ribbons flying, the dozen students in Glenbard West’s auditorium looked more like last year’s Beijing Olympics opening ceremony than a summer school class. It might not have been evident, but they were picking up more than a traditional Chinese dance. This summer in a 22-day immersion program, 15 students from all the Glenbard high schools are learning the basics of Mandarin Chinese, the most widely spoken language in the world.