All around the room, there are pictures of the 2020 candidates — Democrats, President Trump and his two Republican challengers — hanging high above the long lines of lunch tables and plastic stools. In less than a week, many of these students’ parents will head to the Iowa caucuses. Some will probably report to this exact cafeteria, an official precinct. Today, though, there are no swarming adults in campaign T-shirts, handing out buttons and preference cards. It’s just a group of 25 13- and 14-year-olds, free to throw their support behind whoever they think would make the best president.