SAN JOSE, CA—Emphasizing the importance of his instructions by raising his voice and repeating crucial points, Leland High School band teacher Jeff Amos reportedly spent 85 percent of Friday’s rehearsal hammering in the dress code for the school’s upcoming holiday concert. “It’s black turtlenecks with full-length sleeves, and they will stay tucked in for the entire time, do I make myself clear?” said the 54-year-old music instructor during a 25-minute aside that stressed how deviations from the protocol, such as wearing sneakers—even the black sneakers that many tried to get away with last year—would land them backstage for the entire performance. “Girls, skirts must be past your knees. And boys, I expect slacks; gray-colored jeans aren’t going to cut it. Under those stage lights, every single person in that auditorium will see you sticking out like a sore thumb. Got it?” At press time, Amos was reportedly keeping everyone in the band room for an extra 10 minutes to drive home how disappointed he would be if, after so many reminders, anyone forgot their Santa hat for the closing performance of “Jingle Bell Rock.”