I remember Simon Carrington conducting my students in the All-State choir a few years back. There were 250 students in front of him and, of course, lots of coughing. He stopped rehearsal and said "you can control your cough. Please don't cough anymore. Its distracting." Suddenly, silence. He was right, the students did stop coughing.
Makes me think about expectations. Which expectations are reasonable? How powerful can we become if we raise those expectations together?